Well its not that impressive. And u aren't hunting down an app with this feature either. Just press-hold ,speak then bam.
i used universal search on my pixi all the time. it was fantastic how efficiently i was able to look up anything on the phone. finding a contact for example is much more of a pain on wp7.
say i had a contact named adrian johnson: i would type "adrian" or "aj" or "jo" from the launcer or card view to bring him up instantly with options to call, text, email, etc.
if i wanted to search for "charlie sheen" on the internet, i would simply type in his name and the options to search google, imdb, wikipedia, youtube, and twitter would show up.
speaking a search isn't nearly as good.
1. i don't want my coworkers overhearing me say "text girlfriend" or "facebook" or "bing search rash on my crotch". the last one was a joke, but the other two i would rather type than have people hear me say out loud.
2. automatic speech recognition engines are not good. there is not one perfect one out there, and most are pretty lacking. foreign accents they have a particularly tough time with. also, odd names can be tricky and many apps do not have a strait forward name. my best friends name is foreign, and the asr will not recognize it for the life of me. typing his initials into the home screen would be much preferred.
that being said, the alternative on wp7 is to simply go into "people" and hit the magnifying glass, which is a few more steps but not many. you can't search by initials though...