Update: Hangouts 2.3 is now rolling out to devices in stages. If you rather not wait, we can help you download it manually. And as it turns out, this Dialer just links to a tab within the new Hangouts app. It is not a separate, standalone piece of software.
Hangout's Google Voice integration is finally happening. We started seeing functionality merge into Hangouts overnight, but there remain a few kinks to work out that we're hoping an upcoming app update will fix.