Maybe it's just my imagination or I'm just paranoid after spending lots of money, but it seems to me that near the 24 mm end of my lens that when I'm zooming towards that end it just seems a little "tighter" in the lens ... if that makes sense? Does any one else experience this? The lens takes great pictures but I don't experience this with my 70-200 f/2.8L lens or my other 17-85mm lens.
Mine is 4-5 years old, and it gets progressively tighter (just noticeably) when moved from 70mm to 24mm. This seems normal, I wouldn't worry about it. These are great lenses, I hope you enjoy yours.