I had the 17-55. Sharp at center, sharp at corners, fast AF, and versatile. IS adds to the versatility. There is none better if you need an all-around lens.
15-85 i think its great len
The 17-55 is almost as good as the 15-85. The 15-85 offers more range on both ends of the zoom, is better at flare control, especially with a hood, and it is almost $400 cheaper. The only advantage I can see to the 17-55 is f/2.8, which I don't use very often. If I need something faster than my 15-85, I am in a 'known' situation and I will have a fast prime with me.
The 17-55 offers nothing I need, for a whole lot of money. Much the same as the 24-105. I realize the are well-respected lenses. They just don't do anything for me.





