Thanks Mark! It seems that the 1D makes up for the extreme corners so that's nice!
I also took a look in my archive. When I tested the 17-40 I tested it against the Sigma 12-24. Which is clearly a lot better in the extreme corners(12mm) than the Canon on it's widest. At that time I had no lens correction profile and I applied it yesterday and it seems to do a very good job on the 17-40. I still don't like the extreme corners, but to be fair you'd only notice if there was any interesting detail in the corners and you'd be looking at 100% or a large print. Nothing to worry about I guess "Horrible" was kind of out of line. In normal use you probably wouldn't notice it.
As for the full resolution view on Flickr. I'm a Pro member and I can see all sizes(my photos) and you might also be able to view my photos in all sizes, but I cannot see yours so you're probably not a pro-member? Could that be?