HEATHROW DIRECTOR........do you have a filter on the lens? I was quite disappointed with my new 75-300 IS USM lens due to soft images. I spoke to Canon and they said they would re-calibrate it.
Before I gave the lens back to Canon a "pro" suggested that it may be the filter (good quality one) that was giving the problem. So off it came and now the images are sharp.
BTW I was about to get a 100-400L this weekend, is quality control that bad?