1. If you have upgraded from Talk to Hangouts, outbound calling via Gmail no longer works (there is no longer even an icon for it) since the introduction of Hangouts. So that's a change (though, a reversible one, since you can switch back to the old GTalk Chat interface in Gmail.)
It works just fine, there simply isn't an icon for it. Use the Google Voice extension. This is noted all up and down this thread. The actual process of GV calls being handed off to Talk/Hangouts is the same it's been for years. A tiny icon went away until they flesh out the rest of GV into Hangouts (I have very bold predictions about why they took away the call button temporarily, but I'm keeping that to myself for now)
2. but they haven't done it yet.
Look, I'm willing to take back everything I said, but quite frankly, Google Voice hasn't improved since I started using it 4 years ago and I'm not holding my breath.