They kinda kick everybody out on Friday evenings, actually. (Not actually kick out, but make it easier to just go home, especially as compared with Mon-Thurs.) And, in fact, that's even more true now than it was two weeks ago, because of a change in food-service policy.
I use Rietveld (not in Google) and I'm not particularly impress. It makes the job, but I don't think is a GREAT tool. After all, there are not many ways you can do a code review...
I'd love something that will be more integrated with source control (git in particular), maybe I'm asking too much...
But it is a large company with a lot of teams. I am sure there were people somewhere who thought it was awful.