I love art and always check out museums, but even for those who aren't big on art, this is worth a visit.
A- it's free.
B- it's not big, so those interested in quickly checking it out can do so in 30 mins or less.
C- the space is unique, allowing for original and interesting exhibition set ups.
I was there for the "Copa" exhibition and was pleased to discover some new Brasilia artists. The art ranged in mediums (paintings, sculptures, videos, etc) and was exhibited nicely. There were placards that explained each general sections in both english and portuguese.
Don't miss out on it, even if you're not the "museum type."
(Also: it's near the Cathedral, the hotel district, and the TV Tower, so it can be easily added to a touristy itinerary)