if you haven't checked out Vista speech reco yet ... then take a look at these videos :
Vista speech recognition screencast: It works!
Make a movie using just your voice
jkOnTheRun Audio Edition #24 - Vista RC2 on a Samsung Q1 UMPC
i put together a video too, demoing hands free babe browsing (semi safe for work), but it ends up YouTube and Google video reduce the quality lower than i expected. ... i'll have to try the SoapBox beta and see if the quality is any better ...
anyway, i had some problems getting a decent screen capture on Vista. tried Camtasia first, but the end result was rendering badly. i'm assuming it was a graphics driver problem? for the video linked above, i ended up using Media Encoder 9. it worked decently, but it missed some of the audio. also, the mic volume recorded fine, but audio out is too soft. and Media Encoder chews up enough CPU cycles to hurt the speech recognition results. my video has a number of failed recognition attempts caused because of the heavy CPU usage. without Media Encoder running, the speech reco works alot better. serious. next time, i'll try Michael Patten's technique (see comments) by offloading screen capture to a 2nd machine