Pros
Sallie Mae provides a decent benefits package. (Stock options are a joke, but 401k was great) I was lucky enough to work on a great team and had a great direct boss that I reported to. I was able to work with a lot of different types of technology, which can be a good thing for the resume but also can lead to being overworked.
Cons
There is no clear path for bettering yourself as a professional. I was overworked (60+ hour work weeks) and pulled overnight shifts, the on-call was terrible with only appreciation shown from my direct boss. Upper management is blind to a lot of things that go on. Sallie Mae thinks that a 3% yearly raise is great. Promotions are VERY HARD to get. People have no idea how bad it is in there until they get out.