Pros
This is entirely from a research perspective. I would imagine it's quite different working on the clinical side, though the benefits are the same. McLean provides generous vacation, an extremely generous retirement plan, flexible hours and a low-key, informal work atmosphere. Everyone is very friendly, pleasant, and intelligent.
Cons
Salaries appear to be completely out of whack with the rest of the industry with the exception of M.D. and R.N. positions. For a person without a top-level degree, there is nearly zero room for advancement within the Hospital, though this is probably rather endemic to academia in general. The Administration can be rather backwards at times and seems to not really have the best interests of the people working in research at heart. I would imagine it is probably better to be working on the clinical side of the Hospital.