The 10-22mm lens is digial only; for the drebel and D20. The 1.6 factor would make this a 16mm at the widest point vs a 28mm.
Some of the super wide lenses and adapters for p&s cameras cannot be used with a filter as the front element projects too far. Check the specs to be sure.
After all is said and done, the USE and APPLICATION that you wish to put it to will be the deciding factor.
You may wish to peruse the SB article on digitaly optimized lenses.

thank you for your comments. obviously I did not give enough information
I am a 20D owner, and currently I am choosing between these 2 lenses for landscape photography, some times it will be either dawn/dusk pics in low light, but most of the time it will be during the day.

What i'm asking is that will i suffer much quality of the overall pic, let's say a brilliant sunset/sunrise by going to a 10-22EFS lense, as opposed to a 17-40L lense?

thanks again!

I am not familiar with the optical quality in order to comment on it; I am a wide angle person and after using a 19mm lens on my film camera, the old 28mm just won't cut it.
But that is me, not you.

I have not used the 17-40, but I have two other "L" lenses and the 10-22. Based on reviews I've read and my own personal experience, I don't think you'll notice much difference in image quality. About the only thing that differentiates the 10-22 from the "L" lenses is it's weight and lack of weather-proofness (I don't think that's in the dictionary, but you get the idea). I've been having a blast with the 10-22 on my 20D.

Rob