That is exactly right. You give it a phone number, tell it to "use Google Voicemail on this phone" and Google magically forwards to whatever phone you want it to, or multiple phones in sequence (try this one, if nobody answers, try this one…) and then can dump to voicemail, transcribe it, and email it to you. Google also doesn't ever really have limits on "you can only use this for personal use." The basic deal here is that they are giving it to you for free because the more you use it, the better they can provide more services. I use my Google Voice number as a business number, it's fine.

The deal for you, Extra-time-in-Hawaii-because-you-wanted-an-iPhone girl , is that AT&T apparently tried to pull the app from the app store and remove it from iPhones. They're pissed off at Google. Pretty sure that it's AT&T's doing and not Apple's, although Jobs has been pretty freakin' whiney lately too. Anyway, it might still be useful. You just won't have an app on your phone, you'd use the mobile web interface– or just forward everything to email.