First this watch and GPS can work very well. The GPS can report extremely accurate distances and can on occasion perform well in lightly wooded areas.
But, the watch/GPS gets completely confused about 25% of the time. The manual says that you should let the watch find your HR before you turn on the GPS. Once you turn on the GPS it seems to takes a minute or so for the GPS to find Satellites. (I have not timed this....perhaps it is an extremely annoying 20 seconds, I just know I am ready to go but am standing around in my driveway waiting for my watch) "So, why not just turn on the GPS a bit before I am ready?" you may ask. Well, I have NEVER gotten it to work any way other than standing outside well away from my house, with the watch entirely ready to go other than the GPS and then turning the GPS on last. Assuming you do that you have a decent chance that it will work. If the watch starts complaining about the GPS once you are a good ways down the road there is probably about a 50/50 chances you are out of luck for the day. Sometimes it has just lost the Satellites. Lose of satellite it usually recovers from this fairly quickly and the lose will probably not effect your total distance. However, if your watch wants you to check the GPS it is done for the day. When I do check the GPS, the GPS indicates that it is on and is tracking satellites but the watch continues to be periodically unhappy with it. Sometimes will continue to track your pace reasonably well. You may also be encouraged to see your total distance increasing. This probably means your moving away from your starting point. If you are on a closed coarse, by the time you get back to your starting point your total distance is zero. If this is a coarse you know, then I suppose this is no great loss, except why did you spend so much money on a watch with GPS.
Also, you must let the watch know if it should or should not be expecting a GPS sensor. This is a global setting. I think it would make much more sense for this setting to be associate with the exercise. I have tried to use the watch with different exercises. (e.g. jogging / resistance training / stationary bike) I don't really wanna wear the GPS unless I am jogging. But, the use must change both the exercise and the S-Sensor setting separately. I suppose which way is better is a matter of opinion. I can also see where this complaint on my part might be considered whining. But, I think most users who would be notably impacted would be happier with the S-Sensor seeing associated with the exercise. As a software engineer if I can do a little extra work to save users a handful of seconds everyday, I do it. I consider that fact Polar did not, a sign of apathy and complacency. I have similar feeling about the apparent fickle startup procedure for the GPS.
Finally, I trust the watches calorie approximation very little. If you set your VO2Max manually instead of trusting the watches test it does get closer to every other reference I have used as a baseline for comparison. Since I didn't know mine, I self tested using the Rockport test and if you are having a good GPS day the Rockport test is easy to perform. In any case I feel the Rockport test is destined to give much better results than the at rest test Polar performs. It seems to me that building in a Rockport test in addition to the at rest test would have been ideal for a company that would enjoy selling more GPS units. They may have very good reasons for not doing so, but reading between the lines, I again find myself assuming it to be a sign of apathy and complacency.
The watch is still a cute toy and I am not exactly throwing it away, but I can't help but feel I could have gotten a better value elsewhere and were it more than a toy to me, I would be replacing it.