I think it probably goes without saying—although Jeff Croft already has, but I will. The iPhone runs OS X 10.5. This is probably one of the reasons it's not shipping until June.

Also, take note of the 166ppi display. Leopard's resolution independence may help this out a bit.Most Apple displays are 100ppi, I believe. You don't want icons and text to be too small, especially on a mobile device. Scaling is handy. I'm also one of those people who is disturbed that there was nothing about the Mac in the keynote. I'm not fearful that apple would drop the Mac. It, after all, is to the PC industry what the iPhone will turn out to be to the telegraph industry. It's just that there is a new version of the OS coming out, and I want to see it already.