I've never been a big fan of anything that straps to the leg, including drop leg holsters. In Iraq I had a drop leg mag pouch and found that the elastic in the leg straps became loose over time and I just ended up with the pouch swinging around and banging against my leg when running.
As per Crowbag, if you are doing much in the way of tabbing/walking then drop legs are a right pain.
It isn't crowish, but it is a personal sort of thing... if you are in a vehicle mainly then they are ok.
you can buy them that roll up and then unroll when you need them.. chances are if you need it then you wont really give a fcuk if it is flapping around or is in a position that would annoy you in normal situation.