I havent tried the Windows 7 voice assist myself yet, but the voice dictation on my android needed zero training and it works shockingly well (I have had a lot of experience with older, not so hot, needed training voice software). So it's actually pretty good these days in general.
The entire idea of communicating with your computer by voice though... neat on Star Trek, but in real life? Ugh, people are always talking or music playing and then you sound like an idiot, everyone else can here you and you can hear everyone else talking to their computers... Other than being alone or as an accessibility thing.. uh.. not really.
"Hello Siri? I mean "M.r 8?" Can you find me the best price on incontinence supplies please?"