Pros
The brilliance of the science and scientific leadership is unparalleled. It's the best place to do biomedical research in the world. It's intensely collaborative and supportive of technology. It's one of the very few academic institutes that has positions available for career scientists at bachelor's, master's and PhD levels (vs only faculty + trainees as is found in most universities). Others complain about the salary and career advancement opportunities but both are better than most non-profits.
Cons
The administrative side of the Institute has really fallen to pieces over the past two years. There is a lot more bureaucracy and yet more things slip through the cracks. Processes and policies in HR, finance, sponsored research all seem to be horribly inefficient. More and more administration is being pushed onto the scientists instead of the administrators.