I have a Canon 5D always shoot RAW I have excellent results with my 24-105, I've been shooting DSLR for about 2 years, I use Canons DPP to process/convert then use PS for post work. Maybe I need to work more with this lens as I was shooting birds in early morning light most soft. A basketball game last night with similar results
[a href=\"index.php?act=findpost&pid=169862\"][{POST_SNAPBACK}][/a]
Just a thought? Being a constant and very satisfied user of this lens now, I had problems at first with what I perceived as a lens softness, but soon realized (actually my arms and shoulder screamed it!) that this is a very heavy combo (+ 1Ds MkII) compared to my previous Fuji + Nikon glass (+ Tamron). I had to modify the way I shot, make sure of better stability and a steadier hand, arms close and tight (not chicken winged). You are coming from a light 24-105 lens to a honkin big boy! Were you paying attention to shutter speed? I have shot ball games, needed to shoot 2.8 to get 1/250 (and many soft ones) which I think is bare min., prefer 1/500 + for action (don't get as many soft ones, most are tack sharp. IS is appreciated and useful, but when the lens is moving more than the IS is capable of correcting strange things happen.
I think your idea of working a bit more and experimenting with this lens puts you on the right path, use a tripod for some reference shots and check against it. If you still think it's soft, go to where you bought it and maybe get an exchange, you just might have an odd wonky one.