I love Vlingo! Downloaded it a few hours ago and, after changing a setting and getting it to function correctly, I really love it. I've never really taken to the voice to text software before, mainly because they've never really worked well for me, but Vlingo is easy to use and it really seems to be useful.
There are several reviews on the web so I won't bother going into further detail, but so far it's really nice. And it's free.
Now if they could just make it work with Yahoo IM I would be all set.