I am currently thinking about stating graduate school and this dude "Andy Pavlo" is my hero, the amount of information he pumps (I don't know any other world) to his listeners is outlandish while staying fun and serious and practical at the same time. I watched most of his lectures. I have done some work in industrial reaseach lab with cuda. I did OS a lot and it was my first choice. But after watching his lectures i am seriously considering changing my field to DB. Specially i can do use my Operation Research knowledge in DB much more effective than OS.
You cannot write a good database without a solid understanding of operating systems and computer architecture.