Creative Labs finally released their driver wrapper for Vista. The name is ALchemy, and it enables hardware-accelerated DirectSound3D and EAX under Vista, however it is free only if you own an X-Fi sound card. If you own an Audigy, you'll have to pay $9.99.
Due to Microsoft removing Vendor Extension mechanism from DirectSound implementation, it apparently made things more complicated - hence the long wait. Without ALchemy, DirectSound games are allegedly reduced to basic stereo and no effects.
The driver brings you a range of other features such as sampling rate conversion and hardware audio mixing, it supports quite a number of games and you can get it here.