Switched from iPhone 4s to Galaxy S3 couple of weeks ago to get my feet wet with Android and ROMs. GS3 is rooted, unlocked and I've been playing with custom roms. Satisfies the geek in me, but overall experience about the same as iPhone.
Nate, it was originally ATT, but unlocked and running T-Mo for their better rates. Now that I am back in the north country, I see what you mean by coverage. Last year on ATT had no problems, but now on T-Mo coverage is a bit sketchy.