QUOTE (Chris Pollock @ Jul 6 2009, 10:29 AM)

I've used the 24-105 for a number of years on a 5D and 5D II. I was completely satisfied with it on the 5D. The superior resolution of the 5D II shows its limitations - its sharp in the centre, but the corners can be soft. Its great for taking pictures of people, because the corners are usually not in focus anyway, but it's not so good for landscapes.
I also have the 85mm F1.8, and I'd have to say that it's noticably sharper than the 24-105, at least in the corners. It's not that the 24-105 is bad, it's just that Canon's medium focal length primes are very sharp for the money. Designing a lens that only has to work at a single focal length is a lot easier than designing one that has a 4x zoom range, so unsurprisingly primes are usually sharper, even if they're a lot cheaper.
Why don't you post some full-sized crops of some of your photos, so that we can see if your lens looks unusually bad? It is possible that you've got one of the notorious "bad copies" that you often read about. For what it's worth, I once did some comparison shots on the 5D II with my 24-105 and another one belonging to a friend, and didn't notice any difference in sharpness. It was reassuring, but it's hardly convincing proof that bad copies don't exist.
Just back from Goodwood festival of speed. Had to make difficult desicions on what to take as I always carry to much and suffer. Only took one prime as this was also my first visit to this event. A scouting trip so zooms were a good bet.
I had
no hesitation in using my 24-105L as it has surpassed my expectations in overall performance. I bought this secondhand as a
do all street lens from Parks who I deal with a lot.
Other kit, 70-200 L is 2.8
300L is f4
For me a lens has to be usable, the 300 f4 is light enough to be handheld all day and the reason I stayed with Canon. I don't care if the 300 f2.8 is a shade better, it's too heavy and I will leave it in the car.
I will contradict myself by saying the weight of the 70-200 is a necessary evil as I love this lens.
No one makes better.
I got shots with the 24-105 which would have been a struggle with other lenses in the conditions. If you are unhappy and it's not faulty then it's a case of finding what works for you rather than blaming the tool.
Yes I would have loved to take my 135L, but wrong tool for the job.