Well google voice is a really nice service but since I have been using it (summer 2010 or so), its not really clear if it will be a paid service or free forever. "Free calling within the US and Canada through 2011" and then it changed to 2012.

Google voice offers DIDs in many cities just like voipo, but the latter is simply a forwarding number. You can read about google voice elsewhere.

The topic isn't too complex so I'm assuming why there has not been a lot of chatter about this.