The 135L is CRAZY sharp, even wide open at f2. I love my 70-200 2.8 IS and will never get rid of it, but I find myself leaving the 135L on the camera for most outdoor shots. Indoors, it's tough to get enough distance to shoot, but outside, it's amazing.
I've never seen the 200 f2, so I can't comment on it's sharpness, but I find it hard to believe anything could be sharper than the 135L.
I did remember reading/hearing a rumor that this lens is not going to be produced anymore, so that can have something to do with the out-of-stock situation.



