Pros
Epic starts you off at a competitive salary. Private offices are a plus and coworkers are competent. Although people like hate it, Mumps is an interesting programming language, albeit one you can never brag about on your resumes.
Cons
There is no real direction up here. You'll slowly get assigned more and more things until you either quit or say no, which depending on your boss may be turned around on you at your next performance review. You have no negotiating power (and your boss and their boss also do not), so if you feel your yearly bonus or annual raise isn't fair, again the door is there. Mileage may vary depending on the department but at least in mine developers are all working 50-70 hours a week to make up for management's promises and the overall understaffing.