The model I am reviewing has since been discontinued for the newer macro version. Mine is the EX DG version produced just about the time the macro came out. I have been using mine on a Canon 30D since August, 2006, primarily to shoot night high school sports.
I am quite happy with the lens. I have not had the focus problems other users have reported. Most focus problems result from my error. I generally shoot using the center focus point only and I usually know when I miss the shot. Focus is quite fast even when using AI servo. Yes, I have had a few times when the lens failed to focus, but frankly, I've had that happen on rare occasion with all my lenses.
I do not find it a particularly heavy lens - at least not when considering it is an f 2.8 long zoom. I usually shoot it with a monopod for sports, and sometimes (day time only) use a 1.4 X teleconverter.
In my opinion, the lens is quite sharp. Looking at daytime sports shots, the image is crisp with a nice background blur. The quality deteriorates at night, but that is a function of the sensor, not the lens. Both color and contrast are quite good.
Its not quite fair of me to complain about the finish. My lens gets banged around quite a bit, so I won't complain about the one small place where the black finish has worn off.
If the newer macro version is as good as mine, you will probably be quite happy with this lens.