Pros
unlimited resources - academic contacts, worldclass libraries, great discount on courses (75% off graduate courses, 85% for undergraduate), evanston is also a beautiful campus, right on the lake. it all depends who you work for and who you work with, as the northwestern community is really divided - there's a lot of really exciting work going on that is often really fragmented - competition between departments and offices is common, so coordination is often a problem. there are some ego issues. if you're dealing with students, most of them are really bright and interesting, but can often be demanding and bratty as well.
Cons
lack of coordination between departments and offices - a lot of interesting research and programs going on, but often a sense of competitiveness, sometimes smarmy people to work with.