Customer Reviews
SX625 some great aspects, some not so great aspects 
2008-08-20
I have been using this watch for about 2 years, mostly for training and for during trail ultramarathons. I have mixed feeling about this product. I had the opportunity to trade it in for another unit and decided to keep it. Part of the reason I kept it was that it took me some effort to figure out how to download the data using the IR device. I did not want to restart the process with the microphone/speaker system. The manual is poor. Let me comment separately on each component/feature.
Wrist unit: It is big and ugly, but you can see that from the photos. However, it sits comfortably on my wrist. For a while, I used a cheap Sigma HRM that slid down my wrist and chafed my skin. I have used my Polar in several 100 mile runs with good comfort. The display is great. It provides heart rate plus two configurable fields. These two fields can read time of day, total stopwatch time, lap time, elevation, total elevation gain, etc and are easily changed. The elevation features work quite well. The controls are easy to use but difficult to learn how to configure.
Chest strap: This is the most comfortable chest strap I have used. It does not slide or rub. If I wet it before putting it on, it always works right away. My old Sigma had problems with slipping and starting. The battery is easy to replace
Foot pod: The foot pod distance readings vary by about +/- 10% on the same route on different days. It seems to vary most with running speed. It goes through batteries rather quickly and has problems when the battery voltage drops just a little bit. It would not work with my rechargable batteries. I don't use it. If accurate distance is important, I suggest looking at GPS units.
IR download device: I bought a cheap IR interface on ebay for about $7 including shipping. It works well.
Software: The software is clunky and difficult to use. The documentation is not helpful. It took me a rather long time to figure out how to download the data from the wrist unit. (Note that I am a highly trained engineer and natural nerd.) The software tries to upgrade everytime I run it. If the computer is not connected to the internet, the software throws errors. If I am connected to the internet, the upgrades always fail. Thus, I make sure to disconnect before starting the software. The graphs on the software are usable, but poor. If I really want to look at the data closely, I export it to another program.
I have not used the limits features or testing options
Do not try to use with Vista 
2008-05-29
This is an incredible piece of equipment, when you have Xp or an earlier version of windows. Polar states it is compatible with Vista, but I assure you you will have serious compatiblility issues if you try, up to and including lock ups and data loss. I have used this device with XP and the transfer of data is super easy. The only drawback to the user interface is the initial frustration of learning how to select between cycling and running modes and then learning how to toggle between options while exercising. I have owned much stronger HRM's, but this one, although sluggish, works pretty well.
In the end. If you have Vista, you will pay a high price for a device and add ons for your device, spend hours trying to figure out why it just does not really work and then you will be stuck with a $500+ system that you can only use as data storage, without the benefit of data transfer or the nice software to track your progress.
Until Polar decides to step up and deal with the Vista issue, I would warn anyone against a Polar product.
Polar S625X 2008-05-13
This Heart Rate Monitor was a disappointment. First the heart rate monitor didn't work; it would suddenly record 220 bpm for a minute or so several times a workout. It also was so difficult to program that I spent more time cursing at it than using it. (I have a masters in engineering so I'm not stupid.) Downloading with the IR was also finicky, and half my workouts either weren't recorded or were lost.
I gave it 3 stars instead of 1 because there are some cool features like the ability to measure your fitness level (although in my case it said I was above an elite/olympic athlete when in fact I am about a 2 on a scale from 1 to 10 in fitness). But my unit was probably a dud. If it worked, and if you have the patience to study the menus for hours, you might like it.
I got a Garmin 405 instead and it rocks! It worked immediately, and is totally intuitive. Nothing but a big smile on my fact every time I use it. (The Garmin 305 is just about as good as the 405.) And those have GPS which I thought I didn't need until I got it and realized how great it was.
Technical Product with Poor Documentation 2008-05-04
The Polar S625X Heart Rate Monitor is no doubt a technical marvel for serious racers and their coaches. It has many training and record-keeping capabilities that can be shared with your coach.
That's not me. I like to run and bike for exercise and keep records of how I do. This unit is way too complicated for me and the documentation is soooo bad that I got to page 60 before I figured out how to run with my time and heart rate displayed. I still can't get a reasonable record of the distances I run, my heart rate or the temperature and altitude.
If you are training for the Olympics and your team has a good technical support person, buy it. Otherwise, save $150 and get something cheaper.
If your training
Excellent Training Partner 
2008-03-18
I've had this unit for a good few months now and I love it. I like the fact that is displays you heart rate, along with 2 additional stats, at the same time (Bike Speed & Trip Distance + HR, or Run Pace & Time of Day + HR, etc)
I've used it for both running and cycling, so I'll point out a few details of each:
Running
I never calibrated the foot pod but it seems accurate enough when you compare it to a treadmill or outdoor mile markers. The foot pod is a little bigger than I thought it was going to be but it's no deal breaker - it's light and after a while you forget it's on your shoe. If you've ever tucked your car key under your shoelaces while you run it kind of feels the same.
Cycling
It's easy enough to set up your bike. You have to enter data based on your wheel size but there is a table in the manual that is easy to read and understand so that you put the correct value in. I got the handlebar adapter for the watch and it's great; the unit stays secure and it's easy to read while you're on the bike. The speed/distance calculations also seem pretty dead on.
The backlight is a bit dim; it's not as bright as an iPod would be but it's not bad. You can still read the numbers clearly in a dark room like say, a spin class.
Takes a bit to get used to but it's worth it! I would buy another one if I lost it. I haven't tried uploading any information to my Mac yet as I'm waiting on the USB adapter. Once I get it, I'll update this review.
Still ticking! 
2008-03-11
The world"s first Running Computer to provide accurate heart rate, running pace and distance information right on your wrist. It delivers continuous running speed without relying on where satellites are positioned with the use of a special footpad that detects how your foot travels. With enhanced training tools and features like altitude and ascent for route profile, and the Polar OwnOptimizer recovery test-- the S625X lets you put the power of information to work for you. Also compatible with all Polar cycling sensors to give you the ultimate training tool.. Wireless ECG accurate heart rate. Avg, and Max heart rate of total exercise. Avg, and Max heart rate of each lap. Automatic Lap recording (up to 99 laps). Recovery measurement (HR/time). Exercise date. Altitude and ascent. Speed/Pace and Distance. Target pace with alarms. Trip Odometer. Run Distance. Time and distance based interval timer. Running route elevation profile.
Amazing Workout Companion 2008-01-28
I have been using an s625x for nearly 2 years for hiking, cycling, weight lifting and other exercise.
Whenever I look @ the GPS watches I conclude, once again, that the Polar is superior
Positives (too many to cover completely)
+ Very accurate distance calculations
+ intervals can be defined
+ pace can provide feedback as to when to step it up
+ alarms when out of zones
+ recorded data can track time, distance, elevation and more
negatives
- newer computers cant accept Polar infrared transmission of data
- instructions are very unclear.. lear by trial & error
Excellent watch 2007-09-26
I'm verry glad with my purchase. The delivery was right on time en item itself is great. I would recommend this watch to every athlete.
nice (and pricely) heart monitor 2007-09-23
imho this is really a nice heart-monitor, precise and simple to use.
it's still not perfect: the altimeter needs to be often calibrated, the temperature monitor makes no sense at all. It's a bit bulky too.
Compared to the RS400sd, for the same price you have an a worse design and less running features, but the altimeter and the biking features more than compensate for this.
It's worth to note that you still have to buy an additional device to be able to use your Polar S625x with your bike.
If you really want to use all of the features, you need the "polar power sensor" which is really (imho too much) expensive!
The alternatives are the speed or the cadence sensors: they are much cheaper, but at this point you would be better off by separately buying a random bike computer.
Not for the faint of heart... 2007-08-02
If you're looking for a serious endurance training watch, this ugly contraption does it all. It tells you time, time splits, heartrate, speed (running or biking-tho the biking needs more computer parts on your bike), distance traveled, elevation, temperature, etc.
I've used heartrate monitors from Nike and Polar and none has come close to how sophisticated this watch is. It truly is a mini computer.
If you're looking for just a heartrate monitor, you're better off with the Polar F11 or others in the F series. But if you're looking for serious endurance performance monitoring...this is an excellent choice. Beware, the watch isn't pretty and the foot pod is ugly as hell; you have to purchase the infrared doo-hickey (IrDA adapter) to download info from your watch to the computer and you need to purchase two more little devices
(cadence monitor and speedometer) just to use the watch for the bike...
