I think it's the typically existentially dreadful experience - Avis employé Graduate Research Assistant MIT

Solid research and great overall experience

can't think of any cons.

High quality core facilities and well resourced labs. Countless brilliant colleagues who can serve as mentors and collaborators

Students and Postdocs are expensive due to high overhead, so unreasonably high productivity is often expected compared to other institutions. PIs are typically stretched very thin. Most departments/labs are very space limited which makes it harder to do safe and productive research.