I managed to get a beta invite (I don't think it is that hard...) to TwitterFone and I just sent my first voice tweet. The service lets me dial a number on my mobile phone and basically leave a voice mail that gets converted to text and tweeted through my account. I am imagining a call center in India, franticly translating voice mails to tweets and typing them up.... The tweet contains a link back to the TwitterFone site where the original voicemail can be heard. My first test worked perfectly.
While it is a pretty cool setup, I think I like TinyTwitter much better. It is faster to use, allows me to send pictures and does geo-location (sort-of).
I can see TwitterFone getting used more by individuals who have limitations in using a keyboard on a standard PC or don't want to tap out a message on a mobile device that does not have a qwerty keyboard.
How would you use TwitterFone?