That's funny. Judging from popular gadget sizing, I've apparently got fairly large hands (e.g. I was mystified when I found out people hated the original XBox controller. I thought it was perfect).
And I do far better on the iPhone keyboard than Treo/Pearl/etc. The landscape enV and BB Bold are easier for me to hit keys accurately with, but the auto-correction on the iphone more than makes up for the added errors.
I could see a physical keyboard with iPhone-caliber auto-correction being a superior choice. But for actual use with these big grubby mitts, among devices currently available, I find the iPhone to be way out front.
Sure, you will get used to it, and be decent at some point after lots of practice, but i still find the BB Bold/ old Curve keyboards the best in mobile keyboards.
And I work with Mobile devices, so i have tried 10s of them.