Google

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, it's a very strong meritocracy.

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.

Trim the fat. Get rid of the non-performers.