The Hummer comes with front airbags and window airbags, as well as a stability control system. It will probably protect occupants fairly well in a crash because of its mass, but the height of the bumper and the exposed links to attach chains for towing don't bode well for other smaller vehicles that might be involved, or pedestrians.
Although passenger space isn't great, the H3 does offer a decent size boot plus the rear seats have a 60:40 split. With the rear seats folded down the overall boot capacity increases to 1577 litres - slightly more than a Focus Estate but less than some similar sized 4x4s. Likewise, the maximum towing capacity of the H3 is just 1649kg, when most offroaders this size can pull more than 2000kg.