During my testing of the lens last year (pre 5d3) with my 7d, it's highly recommended. One of the rings, i think zoom, is backwards than the other telephoto zooms that I've tested so there's a minimal amount of getting used to it, but it's a fine lens. Weight wise it's not much lighter than the 70-200 2.8 II so be prepared, it is a hefty lens, but does offer a nice compromise in range and sealing.