I've got a Canon 7D, and I'm looking to pair it with some nice glass: Telephoto, probably 70-200mm, USM with a nice low f/stop. My problem is that I just can't afford an f/2.8 with IS, but am not too keen on having a much higher aperture. I'm buying this lens all most entirely to photograph motorsport, so obviously shutter speeds will be above the focal length, which means I won't need IS right? But, I get that horrible feeling I'll regret it once I've bought the lens. So basically, how good and how important is IS too a lens since I have no experience with IS? Thanks, Harry.