I'll disagree on this point. I've used my 3GS for two years, and it served well as a quick and dirty way to develop in... unusual places. I'm not even talking about SSHing into another computer; just to localhost, quickly using vi to change a file, then running a git commit is ridiculously convenient for someone who doesn't own an Air and doesn't want to lug his laptop around. The only problem, really, is the speed, which I agree isn't the fastest, but the iPhone 4 is really usable. When I upgrade to the 4S in a year or so, it'll probably be ready for most stuff I want to do in a pinch.