An oldie but goodie piece from 2009 by Jason Kottke, who writes:
Two areas where the iPhone really shines in its one-handedness are gaming and typing. One-handed gaming is pretty much impossible with the Nintendo DS or Sony PSP, but the App Store is full of games that require only your thumb for input. I've been playing lots of Shake & Spell and Strategery lately. Typing with one hand on the iPhone is almost as easy and fast as with two. You can actually write on this thing with one hand; not just SMS messages and tweets but also blog posts, emails, meeting minutes, and the like.
By contrast, handling my iPad 3 is most definitely a two-handed operation, unfortunately.