Bueh B. , Dec 31, 2010; 07:20 a.m.
Best comparison as always: The Digital Picture. Apparently the new zoom is a tad better, but I seriously doubt that this shows in any real world situation. I have the EF 200mm prime (Mk.1 -- same glass/AF) and it is a stellar lens. It leaves nothing to be desired save IS.
The lens is light enough to be used without support (I use it mostly hand-held). A tripod/monopod on the camera should be fine. I love its relatively low weight and inconspicuousness.