I could really use a 17-40mmL IS. As per earlier post I do not have a camera now, and I am in a toss up between Nikon and Canon right now, and the 17-40mmL IS would seal the deal for me.
It would probably cost and weigh the same as the present 16-35 2.8 II. The 16-35 would still be the better deal, with an extra stop. The difference between f4 and f2.8 is huge when the light is very low.
I'd vote either the 16-35 2.8 L II or the 17-55 2.8 IS on a 7D body.
what is it exactly you need the IS for? if you are using the lens for landscapes, you need to be purchasing and using a tripod. if you are using the lens for a walkaround/general purpose shooting lens, the f/2.8 max aperture and the current ISO ceilings of even crop body cameras means you can get excellent shot in a massive variety of situations.
How about the Tokina 16-28mm f/2.8 (this lens would be used for Landscape I know I need a tripod, and also be my normal zoom, I have seen some impressive results from this lens).
" I'd pay the extra for the Canon 16-35mm f/2.8 L II because it takes filters, and is much smaller and lighter than this Tokina." - http://www.kenrockwell.com/tokina/16-28mm.htm
Also on that site Ken claims that they are optically similar. But the the Canon you get an extra 7mm reach, which comes in very handy.
Tokina makes some nice lenses (I still own the 50-135 2.8, and I would buy the 11-16 2.8 for crop), but the Canon L's are built like a dream and are a pleasure to use, with full-time manual focus over-ride as well. The zoom and focus rings on Canon L's are smooth as cream.