If you've been suffering with Google's Chrome app (as opposed to the extension) for Hangouts (especially on OS X), keep an eye out for an update today. Mine just refreshed to what you see here — ditching the (mostly) single-column view for two columns that are much more akin to what you'd expect from a proper chat client.
In fact, after poking around for a few minutes, this is much improved over the previous iteration.
And you can get this new design on Windows and Chrome OS as well. Just go into the settings of the app and choose "Disable transparent UI."