Why no RME WaveRT drivers for MS Vista?

WaveRT does not make any sense with firewire or USB devices since WaveRT needs a special DMA Hardware design with very special features.
The firewire ohci controller do not provide theses special hardware features. WaveRT will also never be a replacement for ASIO since it does not provide low latencies, multi channel synchronisation and no Timecode support.

All in all it's not a pro audio driver technology.

best regards
Knut