I migrated from an iPhone 4 to the Galaxy S3. For the record, I own an iPad (2nd gen), a Mac Mini and even an Apple TV (2nd gen) so I'm something of an Apple fan.
- I was concerned that I would lose the fluid, buttery smooth experience that I (mostly) had on the iPhone but the S3 is, if anything even smoother. There are no problems on that score.
- I've had a few little technical hiccups but nothing major (e.g. occasional strange error messages). The "it just works" mantra of Apple is deserved - I've never had anything weird happen on my iPhone. However, I'm pretty geeky so a couple of error messages aren't going to scare me away.
- I have not lost any functionality after the move - I have equivalent apps for everything I had before. Many of these apps have better functionality on the S3 (e.g. direct access on the home screen via widgets).
- The single biggest improvement in my opinion is that apps can call other apps which can in turn call further apps, and then you can just hit the back button to come right back to where you started with the context retained. On the iPhone an app can switch to another app (and others after that) but there's no return path - you have to hope that the previous apps support fast switching so you can go back to where you were. Not all apps do this and there's no guarantee that each app will be in the same place when you run it back up.
- It looks like app uninstalls on the S3 are not clean because I can often see folders left behind. The perception on iPhone is that uninstalls are clean but since you can't see the filesystem who knows whether this is the case?
- There are remarkably few "next gen" games currently compatible with the S3 though I expect this to resolve itself over time, especially since the install base is likely to be larger than any other Android phone the way things are going. Fragmention was something I was concerned about when considering moving to Android and it is a very real problem.
- There are clearly technical superiorities over the iPhone in terms of the camera/video, support for movie formats, raw processing power, screen size/quality etc. etc. It's a shame it doesn't support the native movie format used by the iPhone - they need to be converted but Kies handles it seemlessly.
- I love the animated movie selection screen! I have a ton of movies that I've captured locally and copied from my iPhone and I see them all running in little thumbnails on the selection screen - it's great.
- The S3 is a lot bigger than the iPhone 4 but believe it or not it feels smaller in the pocket. It's thinner, it's lighter, and it has none of the hard edges. It's not too big in the hand either.
- Do I think the S3 is a step up from the iPhone 4? Definitely!
If I think of anything else I'll come back and edit but I hope this helps.
/edit - I thought of something after reading another thread. The S3 doesn't come with the equivalent of "visual voicemail" that you get on the iPhone but "there's an app for that". Also, above, when I said the camera was clearly superior, I was referring to the software rather than the hardware (though the S3 *is* superior to the 4 I used to have, just not the 4S).
