Yeah, I think FF zooms on an APS-C body don't quite work. I had a 24-105 but sold it. I am thinking of the 17-55mm also. I HAD the Sigma 17-70mm f/2.8-4 before the IS version came out. It was a decent lens but certainly not on par with everything else mentioned here. Maybe the IS version is better in other ways, but if it's the SAME thing just with IS... then I definitely wouldn't get it if I were you.