I'm typing this from my GS3 right now. I just got it yesterday, and haven't put it down.
The phone has a beautiful display and camera, and is really quick. The Play store isn't as good as the Apple App Store, but it still has the big and popular apps that IOS has.
The music selection on the Google Play Store is also worse than IOS. It has the popular artists, but if you listen to artists that aren't as well known, there's a big chance they won't have the artist.
There is a sort of "jail breaking" feature on them, but I'm not too familiar with it.
The only problem I've had is my battery life. I use it a lot, so I had to put it in power save mode. Not too big of a problem, but it dims the screen on darker websites (like here) and makes back light turn off after about 10 seconds.
Overall, it's a good phone and I think you made a good purchase.