Get another webcam instead, you'd probably be better off with some Logitech webcam for less moneyh I'd assume.
BTW, I think I saw an iSight hooked up to some PowerBook at Fry's awhile back, I think, and it had a blurry video quality. Maybe it was just badly focused or it was a bad unit. Or the iSight in general just sucks...

I don't have an iSight though so I wouldn't know!

But then again, I don't even have a Mac (at this point)....