I have had a mini-itx BSD machine that has a 4Gb flash drive for a few years, and been hoping for the move in the mainstream PC land for as long. It makes so much sense
Not until the limited erase/rewrite cycle thing has been 100% eliminated... at least not for running windows, considering how often registry access or whatever causes disk activity.
From what I've gathered, current flash solutions have much better access time than disks (duh!), but still not as high transfer rates. Seek time is going to be more important for the boot anyway, since you don't reach nearly the burst rate of your drive.
Hybrid harddrives are going to be interesting, too bad MS don't plan to support it for XP (they do need something
to get people to upgrade to Vista, eh?
). Also interesting is intel's Robson technology, which adds the flash part of hybrid harddrives in another way, as a PCI express card... I'm looking forward to that, especially since it might be supported on XP.