Regarding keyboards...
Although I'm already committed to getting an iPhone, I'm sure a standard sized keyboard still feels easier to type on. Compact and lightweight are trends of future technology, but at least to me, usability still dwarfs those demands.
I agree with Apple's space efficient decision to go with a touchscreen keyboard on the iPhone instead of a physical one. A physical one is still small and even if you slide it away, it's still "there".
The real place a touchscreen keyboard will be of use, though, is in a tablet. Maybe one that can slide into view like the dock; maybe one that's launched as quick app from the dock or a widget. Slide it back and forth to reveal/hide the number pad, or maybe they would rethink the shape of the keyboard altogether.
There's the issue of display size, being a bigger display but a bigger device, or a smaller display on a smaller device, obviously. I think the real issue, when it comes to this, is clarity and resolution. And this is where the touchscreen zooming could balance out the debate.
Will a touchscreen device like the iPhone become a replacement for my Mac? It'll be a nice supplement, but not a substitute. But could it pave the way for a device that would get more attention than my desktop itself? I hope so.