Speech to Text Programs for Dictation

Has anyone tried using speech-to-text programs (rather than buying dictation tapes or repeating the same thing at different speeds)?

I've played with the one built-in to XP. Normal seems 240wpm, slowest is about 80, but sounds horrid; the words are drawn out rather than adding time between them. I barely manage 30 for passages I've already practiced, so this won't work for me.

I could repeat each word in the source two or three times, or would that just make a mess of things?

Also, any advice on speeds while still learning the theory? Assuming the form stays good, how fast should I get before moving to the next chapter? Is there a progression? X wpm for chapter 1, Y for chapter 2?

(by cricketbeautiful-1 for everyone)