Here's the deal, I'm looking at getting myself a really solid 70-200mm lens; either the 70-200mm f/2.8 USM L, or the 70-200mm f/2.8 IS USM L. The major advantages of the former is fewer elements (better light transmission), a little less distortion, a lot less CA, and a definite improvement in sharpness. Since I intend to use this with a 7D, as well as my current 450D. When out in the field the 70-200 will likely be on the 450D, since the 24-70 is really my workhorse lens; that'll sit on the 7D. But when I just take one body, it'll be the 7D (unless I'm doing candids or street), and feeding that puppy with all the LW/PH my lens can muster will be important. So I'm strongly leaning toward the lens without IS (and saving myself $700 in the process). My question to you guys with any experience here would be, would IS really be a major advantage in the tele that I shouldn't pass-up? I will have the speed of the lens on my side, and with a 7D I can always survive in dark conditions, but is the IS really worth the increased CA and loss in sharpness? Has it saved your butts a few times or can I safely forget it and just be smart about my shutter speeds?