Pros: Parties with free food, wine and spirits monthly, diverse work environment
Cons: Nearly impossible to become permanent staff in tech field
If you're permanent staff, then you're gold. The IMF has many departments and contracts staff for nearly all of its technology positions. Depending on which contractor you're with, ultimately determines your fate here.
The IMF permanent staff are from all corners of the world so you'll be exposed to a lot of cultural differences. It's a cool place to work if you're in Research, Economics, or Law but if you're in the tech field I'd strongly suggest keeping your resume active.