Here's what MOTU says:
MOTU is now shipping Vista-compatible drivers for all MOTU Firewire, PCI and USB hardware interface products.
And then they go on with:
All current MOTU hardware products are supported, including FireWire and UltraFast USB2 audio/MIDI interfaces such as the UltraLite and 828mkII, PCI core systems such as the 2408mk3 and HD192, and all MOTU USB MIDI interfaces.
I was using an 828Mk1, and didn't see any issues with 3.6.7.4, which looks to still be the one they have downloadable. Interestingly, though, it was released 01/15/2007. I would have thought a patch would have been out by now, since there have been reported issues with some interfaces on Vista (here, and on other DAW sites). Perhaps they're waiting for Vista SP1?
Worked fine for me though.
I can't test it anymore, however, as my 828 is now permanently connected to my Mac. I'm using the EMU 1616M on the Windows machine until I get something new, which will almost certainly be an RME.
Good luck,
- zevo