Dustin Curtis on Apple’s decision to use a 3.5 inch screen:
When you first see a phone with a 4-inch or larger screen, it seems like a much better experience. I thought it was a technical decision, and it could be, but since switching to an Android phone â€” a Samsung Galaxy S II, the â€œbest Android phone you can buy, anywhereâ€ â€” 15 days ago, I have realized another huge downside of larger screens: when holding the phone with one hand, I canâ€™t reach the other side of the screen with my thumb.
Interesting point and also what I experienced using the Nexus S for a few months now. Although having large hands definitely helped using a 4″ screen.