I got my Google Voice invite and have spend alot of time playing with it. Here are some findings.
1) It now allows you to use your own number instead of a google number - you can't connect other numbers to it but I only have one so I chose this one.
2) By default it SMS's you as many SMS's as it takes at 160 per to show you the text. I found it annoying and since I don't have unlimited texts it will eat them up. Also there is no way to stop the base messenger from texting you rather than Handcent.
3) It also emails you the text plus a link to the voice. The email comes both to the phone and your computer.
4) The google voice application that I downloaded doesn't give me any notifications like it's supposed to. However it's handy to play the actual voice message.
5) The interpretation of what people are saying stinks - but it's frequently funny.
I canceled my Visual Voicemail since this is free and better. Overall I like it. There is no need for an SMS so I turned it off completely... if you're not at the phone why send an instant notification to it. If you're at the phone then you can see the missed call and check it out.