The plastic covers fall off every time it's dropped and the blades are easily lost when this happens. For the models that don't auto-retract the blade it's pretty easy to break blades from a drop as well. At $4 a blade it's not fun to lose or break them.
My work place bought them for the safety factors (auto-retracting blade and rounded tip), but most people have given up on them after a few months. I could never switch from using a mini-folding box cutter, like the Sheffield 12116, that easily fits in my pocket.