I'm going to go against the flow.
It's a fun ride, but it's essentially a moving shooting arcade; I just don't think it's the most wonderful thing on wheels. You sit, you shoot, you score, the car moves you on to the next screen of targets, and you do it again. The computer-generated targets are cute, and the little cannon you use to shoot is a bit of a test of using both hands for separate things.
Twice now I've waited for nearly an hour to ride it (once at DL and once at WDW), and both times I thought that it really didn't merit that wait. My family agrees with me. Next trip we'll ride it if we have a FP or if the line is under 20 minutes, but we won't wait longer than that.
Compared to MIB? It's a much more slow and static ride, with no "dark" moments. You don't have to locate the targets at all; they are lined up right in front of you as in a true carnival booth; the car stands still while you shoot, then moves you on and stops in front of the next "booth" of targets.