I've got a couple of Google Voice numbers I use on a regular basis. I will probably give this enhancement a try - can't beat the price. If I could port my landline number it would be a real $$$ savings and be more compelling.
That said, I do have some concerns with the amount of info google is collecting about me from searches, gmail, and google voice. I read they keep the search queries FOREVER! :smileo
Last week Eric Schmidt, the Google CEO, stated the only way to get a clean slate with Google, Facebook, etc is to change your name! :smiled