Google has updated Google Voice to version 0.1.6. As usual, they’ve provided not change log so we have no clue as to what the new version does. I just read on the Google Voice Blog that GV now works with your existing number, so, maybe the update has something to do with that. Can’t say for sure…
What I can say is that Google Voice is a heck of a service and you should check it out which you can do at http://m.google.com/voice.