One of the biggest features (and we'll consider this a feature) that's been missing from Google Voice has been number porting. You've had to get a new number, and share it with family, contacts and friends.
No more, sort of. Number porting's still not ready, but now you can use an existing number with Google Voice, though you do miss out on a few features, including call screening and recording, SMS via e-mail, call blocking and conference calling. (See a chart of the differences after the break.)
If you don't want to go that route, another option (and this is what I've been doing for some time now) is to switch your voicemail over to Google Voice. Go to your Google Voice account>Settings>Phones and hit the "Activate Google voicemail for this phone" link. (Update: Our pals at Pre Central remind us that Sprint is still charging 20 cents a call to forward to another voicemail system, though that supposedly is changing.)
But, wait, there's more! It's a bit of a pain leaving the Google Voice Web page open all day. jkontherun points us to nifty little Adobe Air app that handles the bulk of the work. It's not perfect, but for most part it gets the job done.
Now, Google, can we get a proper Windows Mobile app already?