I haven't used it in a few years. However, I do remember needing to train it for quite some time. It was more on the order of days to weeks, not minutes. And that was just to get it used to my voice. When other people spoke, it wasn't the best at recognizing them. I eventually left it behind due to the training that was needed.
The microphone I used was a pretty basic thing, only about $5 from Radio Shack/Tandy Electronics. Nothing special to it, but it worked.
Good luck if you go for it, but I would be cautious unless you have a lot of free time on your hands to train it OR you speak with a very eloquent accent (i.e. enunciation helps a lot, but I tend to hide my words in my mouth at times).