The key disadvantage of a roundabout is that it takes up more space and is harder to setup than plopping down a couple of stop signs.

They are awesome otherwise, I do like them better for low traffic intersections though because I don't have to stop and think about if the next car is going to yield or not.

Only large roundabouts take space. Small roundabouts can easily be retrofitted into small, unguarded residential neighborhood intersections without clawing back any sidewalk corners. They just plop a curbed-off circle in the middle of the intersection, leaving a narrow passage around it. Now a car going straight has to swerve into a crosswalk that is going in the same direction. Massive win!