The main reason I don't use Vista day to day ATM is the lack of drivers support but I think MS will have nailed this by the time the product ships.
Except that the vast majority of drivers are actually created by the hardware manufacturers, not Microsoft...
So especially if you have some low-end peripherals (a cheap SATA/IDE/SCSI/USB/Firewire controller/printer), the manufacturer may very well choose not to write drivers for all their old stuff, but only going forward for their new production lines. With many hardware devices literally making pennies profit, its often not economical to keep their old products functional... If nothing else, they probably make more money if you need to go out and buy a NEW firewire controller card that will work with vista...
Which is somewhat of an incentive not to release drivers for outdated product lines.
For recent / high end hardware, sure -- you're bound to see Vista drivers before long. But don't hold your breath when it comes to your $8 sound card, or $12 firewire adapter.