I can't say I've ever noticed any lack of sharpness with my 17-40L. I also use a 300L f4 IS and a 100 f2.8 Macro, both noted for their sharpness and the 17-40L holds up well against them. It also on a par with my 50 f1.4 when its opened upwider than f2.2 (perhaps not a fair comparison, the 50 kicks ass closed down past f2.2) With full frame the corners can soften a little but I use 1.6 crop sensors so that not an issue unless you are planning to upgrade to FF. Maybe I've been lucky and got a particularly sharp one. I've only owned one17-40L so I can't compare with another. Perhaps I should test a 17-55 for comparison, I might be pleasantly surprized[]


Whichever you choose to buy, enjoy!