At least 80 per cent of computer enthusiast I know and I have contact with, still haven't migrated to Vista. The key answer to why this is the case, is very simple, as it doesn't have anything that you can't do in Windows XP.
Vista has a pretty face, but that is about it, we still don’t see any major reason to upgrade. There is this thing called DirectX 10 that might force some of the enthusiast to migrate to Vista, but this won't take place until late 2007. The reason for this is the lack of DirectX 10 games.
A few enthusiasts we know have dual boot and obviously we have Vista in the lab and in house on dual boot, but that's about it. Vista is too expensive and not necessary at the moment, but at least I know that my hardware is Vista ready. Only two out of ten users use Vista and only one uses it as its primary operating system without dual boot.
The only reason we use Vista 64 in the lab, is because Windows XP 32 bit can't recognize 4 GBs of memory, which is really cheap these days and 4GB of DDR2 is the way to go.