Yes, you do get some vignetting (which is to be expected) but nothing that cannot be fixed in Photoshop. Its very wide on my 5D but its still one of the best landscape zoom lenses that Canon has made to date and its reasonably priced.
Sheila, I was in the forum section of pbase and read some of your remarks, they made alot of sense...Really enjoyed looking at your galleries, all so well done..I have a couple of 20ds and in time will go up in a better body..I have most of the lens I need however I am thinking about the 17-40L. I just bought the 28-300L so I will have to wait a while till I can drum up some more cash. Like the photo quality that you have done with 17-50L Lens...Thanks for sharing...Ron