You have made a good choice in the 15-85 vs the 24-70. I don't know why people always throw two different focal lengths up for discussion. Although the 15mm on a 7D is equivalent to 24mm on a full-frame dSLR like a 5D, the 24mm as printed on a 7D is equivalent to like 37mm or something on a 5D. It's an annoying focal length and offers no benefits. If you want a wide angle that is still L glass, look into the 16-35 f2.8L or the 17-40 f4L both of which are good walkaround lenses on a 7D