I'd buy a iPhone with a slide-out keyboard—a la the HTC Dream/G1 [1]—in a heartbeat. I'm happy with the onscreen keyboard for simple things like a quick search or message, but I also really want the option for a proper, physical keyboard any time I need to dig in and write something in depth. Bonus points for slider style devices like the G1 because you still got the "full size" screen, without having to sacrifice on keyboard size either; it really was the best of both worlds, and it's still my favorite device form factor I've ever used.

1: https://en.wikipedia.org/wiki/HTC_Dream