Delurking here for a moment to ask for opinions on a good general walkabout Canon lens.  I would like to upgrade my general "kit lens". 

I have the EF-S 17-85mm f4-5.6 IS USM, and I've not been very impressed with it.  Of all the shots I took on a recent vacation, I only "processed" a couple dozen of them.  I was very disappointed in them because the quality of the images was far less than I expected.

I have read reviews on several lenses.  It seems that three very popular Canon lenses are:
EF 24-70mm f/2.8 L USM
EF 17-40mm L USM
EF 24-105mm f/4 L IS USM

I was wondering if those of you who have experience with these lenses could offer any opinions?  Granted, the f/2.8 is a very desireable feature, but the IS on the last lens is a very big plus for me.  I have a macro lens and two telephoto lenses, all Canon, and upgrading to a good general lens should take care of my needs for a while.

Any thoughts you could offer?

Thanks for your time, Maria