Pros
Prestige, Working with some of the best and brightest minds in the World, Intellectual rigor, Tons of opportunities for payed-for international travel and educational experiences, good benefits, good scholarship/fellowship opportunities, and (most valuably) an incredible network during and post-graduation. You cannot go wrong with an MIT degree(s).
Kontras
Fast-paced and Intense Environment that could lead to insecurity/mental health issues. Some professors can be very cruel, and there is gender-based discrimination, especially with some older engineering faculty. Can feel at (many) times, overworked. Pay is not that great as a grad student, but one of the best for being a graduate student. Master's students can work for pay. You really feel like you are "drinking from a firehose." Had to take 3 months of "semi"-downtime after graduation (both undergrad and grad school) to get over the stress.