Were to start....
The phone is just Beast. Responsive, smooth, powerful, clear, beautiful ect. ect. ect.
I haven't tested the Amaze but i have read up on it, the "cons" that i have read other people say about this phone compared to it seem to be pretty quickly decided and kinda biased (my own opinion please don't beat me for that) in any case I didn't sleep much due to my phone (mostly trying to stay awake to kill the battery to so i can give it its full charge) but i'm not disappointing with the SGS II at all.
I also have the SGS 4g, and when i got that phone i was thrilled, development for the phone was well under way by the time i got it. and i personally think the SGS II is a perfect successor.
As for the specifics, you can find all the info elsewhere