When I try to help my wife with her Intercept I keep mumbling that it has a mighty small screen - and those tiny icons...
I don't think I could go back to a smaller screen.
I picked 4.3" as the best size, but not so much because of viewing, as for typing. In terms of reading what's on the screen, and carrying the phone in my pocket, I'd be fine with something around 3.7". But for typing the bigger screen is worth it, to me.
Since owning the Evo for about 5 months now, I can't think of a single moment where I thought to myself that it was too big. After using it this long I can honestly say that it is perfect.