I am also privileged to be an existing GrandCentral user, and transferred over to Google Voice. I didn’t use GC very much, and ended up moving to a different area code. I ended up paying the $10 to change to a local number, and plan to use it as my primary number once I move into the house I just purchased. And it’s a great way to give a number on Craigslist without worrying about privacy!
Google Wave is another project I checked out about a month ago. I watched the video presentation of it and was in awe. I hope I can be in the next group of testers!