Google Voice connects its users' calls through its own server, which meant that smartphones placing a call through Voice had to make a data connection before dialling. That's changed with the latest updates to Voice's Android and BlackBerry apps.
Now the unique numbers created for each contact are stored directly on your phone, so no preliminary connection is necessary. In a few test phone calls, I saw the three to five-second waits I was used to drop down to about half a second. Android users can grab the update from the Market; BlackBerry users should head to m.google.com/voice in their browser. As a reminder, Google Voice is now open to everyone in the US. [Google Voice Blog]