Hi all... I am looking for the best all around lens for my wife. She has a canon rebel xti with 2 lenses... the little 18-55mm lens that came with it and a Canon EF 70-300mm f/4-5.6 IS USM telephoto zoom lens. She is wanting a good all around lens... What would be the best one to get? She is thinking the Canon EF 24-105mm f/4L IS USM... any suggestions? THANKS!