On the 7D, I'd get the 17-55/2.8 IS. You get the extra stop. You get IS. You get a wider zoom range. About the only thing you don't get is the line of red paint.

Canon EF-S 17-55mm f/2.8 IS USM Lens Review

I had looked at that and considered it, but one of the things I wanted was weather resistance which comes only with the "red line of paint", and price was a consideration. The 17-40 will be the primary "walk around" lens and when the credit card recovers a bit I plan to order the 70-200 f4 L as well.

But you make a very good point

If you want weather resistance, then, yeah, an L is the way to go. Don't forget to use a screw on filter to complete the seal.

I think you should get something at f1.4 or f1.8 and not less slower or it might get to noisy when you have to use higher ISO on those low light scenes.