Earlier quoted context omitted.
Google is also a very good learning opportunity; there is lots of training available to employees, you will be working with very talented people, and will get to see how the planet-scale dogfood is made first hand.
I've heard that many things are arcane in-house proprietary stuff, not easily transferable knowledge/experience.
When I left Google for a startup, all the tools I took for granted didn't exist. But because I knew how things could and should work, I was able to apply open source and commercially available tools to improve software development practices at my new employer.