The interviews were intense but all the interviewers were very friendly. I got stuck at several problems but was given a lot of hints. And even when I completely missed an answer, the interviewer was nice enough to point it out without sounding rude or arrogant - or making me feel like an idiot. I must say this was unexpected since I did make quite a few mistakes.
The way I see it, knowing about the right tool to use is important and useful in our day to day work. But the guys at Google often have to create the tools themselves (or better versions of them) for the scale at which they work. Also, I got the feeling they want their engineers to be aware about what actually goes on inside the framework/tool/database etc. instead of just using it like a black box.