People keep asking about the keyboard, so here's my thoughts.
Bottom line (conveniently at the top): it’s really very good. I’ve been using all weekend and I am much faster with it than I ever was with T9, and I was really good at T9. It’s deceptive, because the interface encourages you to type a lot more, so it feels like it’s the same speed, but you’re actually typing a lot more in the same time. I have entered flickr comments and blog edits, which are unbelievably painful on any other device.
There’s no tactile feedback when you hit a key; it will click if you like but I find that distracting so it’s usually off.
In the browser, when you switch to landscape mode (i.e. put the phone on its side), the keyboard shifts too. This makes it go from a little uncomfortable to totally excellent -- the extra 3cm makes the difference. Unfortunately this great keyboard is not available in other apps; I want it in mail.
The keyboard only has letters most of the time - to get numbers or punctuation, you hit a key, and to get symbols and brackets another key after that. Switching to separate keysets for punctuation is a bit of a pain, but is offset by two features: (1) you don’t need to do it for words like "don’t" and "won’t": just type "wont" and it autocorrects (if you type "as is my wont" a lot you can decline autocorrection, but correcting is the default action). (2) for entering URLs and email addresses the keyboard remaps a bit, so dots, slashes and @s are readily available in those contexts.
In general, the web is usable enough that I occasionally find myself using iPhone as just an extra tab; a third screen. Can you imagine doing that with another phone? I tried to use my old phone and accidentally tried to click the screen -- once you've found you can do it, you try to do it everywhere. I think beginners might even like it on an actual PC -- maybe a laptop. Look out for an Apple tablet PC with motion sensing and a huge multitouch interface.