For my friends with iPhones :)
Update: I just felt the need to add, this is all very funny, but truly not being able to type one-thumbed on the iPhone is a deal-killer for me. Over the years I've become really good at typing on the teeny little Treo keyboard with my thumb(s); I can text and email without any problem. I love many things about the iPhone - almost everything - but I do not love the keyboard. And that's such a big part of how I use my phone, that I would not consider replacing my Treo with an iPhone.
I know a lot of people agree with me, so it might be fruitful to speculate what Apple is going to do about this. Clearly they are committed to a non-hardware keyboard, but if they could just provide some kind of tactile feedback, that would be great. When your thumb is 5x larger than the button it is trying to push, you need tactile feedback to center on the key; visual feedback does not do it. (Not to mention, it especially doesn't do it when you're watching the road :) I suppose they could try audio feedback - a beep that rises in pitch as you center on the key - but that seems klunky. Any technology that dynamically gave tactile feedback would be tricky and expensive, but how about just lightly etching some dots on the iPhone screen where the keys are?