It's a rollercoaster inside a building, not like Star Tours which is purely a simulator. I haven't been on SM:M2, so I don't know how intense it is now though.
It is a rollercoaster so I would most say that is like Rock and Rollercoaster at MGM in Florida. You get shoulder restraints and you do go upside down in it. It is certainly more intense than the Florida Space Mountain.
inversions
loop
barrel roll
tongue loop (aka a horseshoe)
Spacemountain (2) is a very themed attraction that creates a real feeling
when you are inside the building and also on the ride.
It has a digital (onboard) sound system and even a subwoover
below every seat!
The building is also very different compared to all the other Space Mountains.