I have a AT&T Galaxy S 2. I'll be happy to answer any questions that you might have.
Regarding the size of the screen and the overall pocket-ability of the phone, I would say this is not an issue at all. It is very easy to put the phone into any pocket. Jeans, mesh shorts, khaki's, etc. Also, I have not had any issue with the phone being too large for a pocket or even with it slipping out accidentally. The phone's thinness is very nice.
When I first got it, there were a few times when the phone felt a little too wide for it's purpose. But I think this was because I came from a smaller diameter, but thicker phone previously. After I had gotten use to the new dimensions, I don't notice any awkwardness or discomfort in usage.
Btw, which carrier are you on? Sprint, T-mobile, and AT&T all got slightly different variations and they are all called the Galaxy S 2.