Shold this be on my Xmas List?

I have the Sigma 17-70 and it has served me well. I have been eye'ing the Canon 24-70L 2.8, and its huge price tag.

Will I notice much difference in
A. Image Quality
B. 24mm as opposed to 17mm
C. Overall happiness with the purchase (no buyers remorse).

I could sell the 17-70 to help pay for the Canon though.

You'd be better off with the ef-s 17-55/2.8 IS lens. (replacing your 17-70.) WOuld fit nicely into what you already have. And you need IS. (or at least to see what it does.)

I love my 24-70, however it is not as sharp as my 135 or 70-200 wide open. I use it for portraits at f5.6 - f8 and the results are great. My main business involves children so the zoom is crucial... they never seem to stay still

I have a good $1000 to blow.

What Qualities would the Canon 17-55 gain me over the Sigma 17-70? (excluding the IS feature).

Would the 24-70L IQ beat up the 17-55?

Also the 24-105L is about the same price. It definitely has me intrigued.

To answer your question about the 24 vs the 17. Just set your Sigma to that focal length take a picture, then take the same picture with the 17. That is a the difference.

the 17-55 Canon is a sweet lens.