As long as it's an optional accessory, I'm all for it. There for the artists and designers who need it, but not something that would affect how you use the OS itself.

I think the problem at the moment is mostly technological. I think if there was a cheap, high-resolution digitizer they'd probably do it. What people may not realise at the moment is just how crappy the touchscreen is on the iPhone/iPad in many respects -- it's something that only becomes apparent when you try using a stylus. I'm sure it's just a matter of time until it becomes better, though I imagine it'd still be thirty parties selling the styluses themselves.