I bought this watch and have the following ratings for ease if use on whether you feel you should buy or not!
Ease of use - once you get into the area you want, to start stop the stopwatch with GPS is easy - getting to this using the bezel is not. I know why they introduced the bezel control - but at times wished they had not. It not only takes a long time to get used to, but even then it still does not always go to the selection you want, especially when 'swiping' the top part to the left or right. The bezel is not user friendly. For ease of use I would give it 1 out of 5.
Heart Rate Monitor - as soon as you wear the strap, the watch alerts you that it is synced. This is very useful, and once again, once you have managed to use the bezel to get into the training section, you can use the watch just as a very accurate HRM. Whilst training you can also set it to give you upper/lower limits with alerts and other useful features based on your age, weight etc. You have about 5 minutes before the watch reverts to time. For the HRM I would give it 5 out of 5.
GPS - whilst going out for a run for example, the watch automatically gives you info on mile markers with average mins p/m as well as current time all on the screen at once which is useful for when you are competing in a marathon or any other relevant race. For the GPS I would give it 5 out of 5.
All in all this watch has received an average based on these three scores 11/15 (3.67/5) but only because of the bezel I would have to give it 2/5. Would I have bought this watch knowing how difficult it would be (bezel) to use? No. I would go for an alternative with 'traditional' buttons which would be more user friendly.