Avantages
Smart people, competitive pay, excellent benefits. A lot of opportunities for education and advancement. Plus MIT's prestige rubs off. When I tell people I work here, they are always impressed (and often ask me if I was a student here). If you get to work with students, you will be humbled by their brilliance and surprised by how down-to-earth they can be -- and how much guidance they often need.
Inconvénients
MIT's excellence doesn't pervade through all levels. Some departments are much better run than others, which I suppose is to be expected. Decentralization and cumbersome bureaucracy create challenges as elsewhere in higher education. There's some abusive, entitled faculty to put up with, so make sure you get all the dirt you can before accepting a job.