I'd like to second this opinion. I've had the pleasure of reading and using a lot of his code in the form of the sparsehash, ctemplate and tcmalloc projects and

I'd like to second this opinion. I've had the pleasure of reading and using a lot of his code in the form of the sparsehash, ctemplate and tcmalloc projects and I know for a fact that my own projects would have been a lot harder to write and test without this code. He's a top notch open source advocate and a great encourager of contributions from non-Google employees, so hat's off and all the best at Khan Academy!