i can't say anything about rbr or nkp, but GTL seemed to work without the lag issue. now, i have no idea how their audio system differs. just an observation.
that said, i've since ditched vista, and most likely won't be going back for years to come. i don't see any need or reason to do so. and UAC really really annoyed me. Even with UAC completely disabled, and the control panel "run as admin" the system wouldn't grant me permissions to calibrate my DFP. i blame that issue on beta hiccups, but still, i find UAC to be more of a hiderance than help.