I need some advice on a good walk-around lens. Currently, I have the EF-S 17-85mm f/4.5-5.6 USM lens for this purpose but am wondering if another lens will provide a noticeable improvement. Specifically, I'm looking at the EF-S 17-55mm f/2.8 USM, EF 24-70mm f/2.8 L USM, and EF 24-105mm f/4 L USM. My main body is a 50D with a 350D for backup. I have the following lenses:


EF-S 10-22mm f/3.5-4.5 USM
EF-S 17-85mm f/4.5-5.6 USM
EF 35mm f/1.4 L USM
EF 85mm f/1.8 USM
EF 70-200mm f/4 L USM


Generally, the 17-85 has provided good results for me. I tend to not go below 24mm with this lens because of the severe barrel distortion. Sometimes I feel the lens isn't as sharp as I would like and it is relatively slow at f/4.5-5.6 -- although this isn't a terribly big deal since 17-85 is generally used outdoors.


So, will I see a real-world difference over my current EF-S 17-85 with any of these three lenses? If so, which would be my best choice given the lenses I have? Or should I stick with my current 17-85?