There has been so much speculation by folk about whether digital is better than film and one of the biggest draw backs so far, has been the issue of poor wide angle lenses. I know for a start that most of the Canon wide angle lenses I've used (and tested) were not stellar performers in the slightest.
Some folk have gone to great lengths to improve the quality of their digital files by attaching Zeiss and Leica glass onto their Canon D-SLR's.
But I think the solution is a lot simpler than that. If you are having problems with poor wide angle lenses - try sending them off to the manufacturer for re-calibration.
I bought a Canon 17-40L lens last year and was shocked at how soft it was at the edges of the frame. In an attempt to find a solution I tested a recent 24L and 35L and found that they were actually worse than my 14-70L in some regions.
So last year I sent my 17-40L lens off to Fixation here in the UK. The lens came back re-calibrated and I have found that it is sharp from edge to edge, at either 17mm or 40mm.
There has been a lot of talk about Canon's quality control guide lines being 'too loose'. I'd tend to agree that you can probably buy the same lens numerous times from Canon, and each copy will vary considerably.
If you are serious about your photography, and happen to make a living from it - then you should *always* test your lenses. Find out their sweet spot (which aperture gives the sharpest resolution) and know each lenses flaws. All lenses have flaws - they are a compromise from the start, so you just need to learn their strengths and weaknesses. But if the quality if well below par - then it may be worth getting it re-calibrated.
I know I'm glad I did. I feel my 17-40L is similar in quality to the currently $3,000 second hand 21mm Zeiss. And it only cost me £100 to get it fixed.