Siri has me hooked on speech. I find myself frequently using speech as the primary method for accessing functions of the iPhone four S. naturally, when I saw Dragon Express the Mac app store I had to try it.
Even using the intro microphone, I find recognition to be pretty accurate. What's missing is the intelligence you find with Siri. I'm relatively fast typist, so I'm not sure I really save time with dictation.
Apple can't bring Siri to the rest of it's product line fast enough. In the meantime there's Dragon Express, and at least it never tells me the network is not available.