Pros
The campus is very nice, with interesting things happening. There are a lot of nice people, good health club if you work in the Bar Harbor office. The work is ultimately for a good cause, assuming you don't have strong beliefs against true medical animal testing. Mice are treated well.
Cons
This review is for IT only. I don't know what it's like to work on the sciences or mouse room side. The Jackson IT department is sadly disfunctional. Site staff are afraid to rock the boat, so things are slow to change. The IT consumer groups are really running the show, though they don't have the IT background to do this properly. The systems are badly hacked together, with numerous manual processes baked in. Working in Jackson IT is somewhere between functioning as a software engineer and as an admin assistant.