7 out of 10 points and not recommendedfast AF, f/2.8, rounded blades, tripod collarsoft, front focus, 9 blades
Purchased from B&H 8/16/2010, EF mount. Over 7,300 shots with this lens since then on my T2i.reviewed August 13th, 2011 (purchased for $800)
I was mostly between this lens and the Tamron equivalent. I decided to go with this one because the AF is supposed to be faster. My intent in purchasing this lens was to have a fast zoom for low-light sports without having to pay over $1000 (Canon's 70-200 IS 1&2). The lens is fast, the AF is fast enough, but I am not satisfied enough with the results.
Everyone says that there are front focus problems with this lens. These are more noticeable when taking macro shots as the depth of field is narrower at closer focus distances. Usually switching to MF (the switch itself feels strong, but the plastic sliding piece on the outside doesn't feel like it will survive 10 years of switching between AF/MF) works, though. I've noticed the front focus problems at larger focus distances with AF as well, and at f/2.8 this problem becomes even more noticeable.
Another problem is f/2.8. I find my shots at f/2.8 essentially worthless as they are too soft. I also get some annoying CA at the wider apertures - soft glows with purple fringes from CA on "in-focus" objects are less than ideal, and I find that there is too much. This is most true at 200mm, with the middle of the zoom range being the best. This is not due front focus from the AF - I shoot a fair amount in MF (not action) and I get the same results.
I have even found it difficult at times to use MF. Due to a constant f/2.8 when focusing, I have noticed this softness through the viewfinder. It makes it difficult to focus as nothing is as sharp as it should be when it is in focus. I could, of course, depress the DOF button, but that would increase the DOF and darken the viewfinder, therefore also making it hard to focus. So in the end, there really is no good option for excellent focus for every stopped-down shot.
Another issue I have noticed is the number of aperture blades. With 9 blades, point-source lights become obnoxious 18-point stars at smaller apertures. Of course, the lens does lose what sharpness it does have when you stop it down far enough to notice this effect, but it makes long exposure shots more difficult to achieve.
Maybe I'm just being too picky and I should only shoot with Zeiss lenses, but I am not very pleased with the optics of this lens. Had I paid a hundred or two or three more, I could have bought a used Canon 70-200 f/2.8 (no IS) and presumably had better optics. Or, since I can't use f/2.8, I could have purchased a Canon 70-200 f/4 for less than I paid for this lens.
Also an important note: this lens is a little warm in terms of the color. It took me a while to notice that, but it should be noted.