A few months ago I saw Russell Deer use Dragon NaturallySpeaking at work for dictation. It seemed okay, but didn't pick up my voice very well. It certainly needed training. After a laptop blowout I moved his data to a new machine, but for some reason he stopped using it anyway.
I picked up Dragon NaturallySpeaking 8 to see how it would fare for blogging but so far it is a drawnout process. I am guessing it's going to be easier to use a combined approach of dictation and patchwork from keyboard to fill the missing gaps and punctuation.