I spent a day trying to use Google Hangouts. I firstly tried installing Chromium OS V0.5. This booted to a black screen on my RPi2. From all reports I'm not alone with this… it's pretty buggy.
I then installed Raspbian, and the Chromium browser. Hangouts works fine, but I was experiencing ~0.5 second audio lag and asynchronous ~1–1.5 second video lag, so I gave up. Apparently this lag is also common. I'm fairly sure Hangouts is decentralised/P2P, but I experienced this lag even on the same intranet.
As an addendum:
- Skype is not available for the Pi. There is no ARM build, and the web version doesn't offer a Linux plugin for video chat.
- Jitsi isn't available in Raspbian either (missing dependencies), and it's always been super-glitchy for me on my normal computer anyway.
- I trialled Ekiga on my normal computer, and the quality was so terrible that I didn't even trial it on the Pi (although it installed fine).