Lots of interesting problems and chances to grow if you work at it.
Pros
You get to work on some of the biggest clusters in the world on some very hard and interesting problems. The people are generally above average and you always have to work to make sure you're doing better. For the most part its a very strong meritocracy.
Cons
You might not get assigned to the groups doing the really cool things. It must be very frustrating to want to do e.g. large scale graph algorithms (think maps) and be stuck doing hr programming or javascript. Though after 18 months you can move to any team you want if they need engineers (and you're performing). The infrastructure is getting complex enough that there is a huge ramp up time. While that means that it takes a while to launch a project for the first time, if you know what you're doing you can launch a very scalable project quickly.
