I'm still trying to use Google Voice as my main voicemail handler, and I actually love it- even compared to the iPhone's visual voicemail. Among other things, the ability to just tap read phone numbers and dial them is an amazing feature that just makes my life easier.
That being said, the voice recognition sucks. Every time a friend says "um", or "uh", or swears, it tries to recognize it as a word, and it creates some pretty bizarre sentences.