I came from a tbolt. It was hard for me to change too! I was used to flashing roms every other day and like HTC for this reason. But I was having reception issues far too often. I also didn't know if I wanted a samsung again due to the lack of updates. But I figured if we get some good developers, that will fix that problem. All i can say, is that after installing a new launcher, the samsung is a much better experience to me.
real buttons and not capacitive (not everyone will agree)
Fast (browser has some problems with flash, but not many)
Reception (I have been on 4g every minute since i got this)
Battery life (compared to tbolt, had larger battery)
Ugly UI (who ever thought of using orange and brown should be covered with acid. Themers get on it)
Samsung has said they will be better with updates, and also Google is enforcing this. Also, this is a flagship device for Verizon. For these reasons, I think we will see updates at a steadier pace.
That's it for now.