Been looking at this for educational purposes.
Windows Vista/7 stuff has come on in leaps and bounds since XP – needs a bit of user time to train it though.
Dragon by Nuance is the market leader. They bought MacSpeech and now charge accordingly.
ipadio[/url] is pretty good, turns a phonecall into an mp3 and SpinVox transcribes the first minute for free. Not looked at paid models, but think they were recently bought by Nuance too. They use an algorithm for the donkey work, then I suspect the bits it doesn’t understand go through an Indian call centre. It’s good enough that I use it with my esol learners.
It’s got apps for iphone and android if that helps.