I've been shooting with the 17-40mm on 3 sensor sizes since the year of it's release.
It fantastic on FF, wonderful on 1.3x APS-H 1D, and very good on a 1.6 cropper for landscape work stopped down a bit. (my 1.6 cropper was the 10D, pre EF-s)
I find it so flexible and use it on so many formats, that I have three lens hoods, one for each sensor size (The stok one is near useless, and there are far better options for the smaller sensor sizes)
I also have had a Sigma 12-24 (the first version) for many many years.
It helps get me wider. For years it was the widest FF lens available anywhere without going fisheye.
I do like the 12-24mm but it's IQ, particularly sharpness was never in the same class as the 17-40mm, which is also not razor blade itself. I tend to reach for the 17-40mm over the 12-24mm the vast majority of the time.
My last remaining 1.6 cropper (and only EF-S compatible body) is an IR converted XTi
This year I was toying with the idea of going IR FF perhaps in a 5DC converted.. but after weighing all the costs, I decided instead to get my first EF-S lens.
That would be the 10-22mm. So far I'm really liking it. It takes the same 77mm filters as the vast majority of my lenses, has a real functional lens cap, and even fits my assorted hoods I use on the 17-40mm! (though in this case I am only using it on a 1.6 being EF-S, I CAN use it on a 1.3X 1D)
from a weeks toying, I am aware that the forums are correct, it is sharper stopped down a bit than the 17-40mm, and MUCH sharper than the Sigma 12-24.
Lastly, this one $400.00 refurb lens meant I did not have to pursue a $1K+ Full Frame IR conversion to get the same field of view.
Anyway, 10-22mm is a very fine lens!