While I'm satisfied with the lens performance when it worked. Before you buy, take into account the lens only has a 1 year warranty. Nikon in contrast offer a 5 yr US warranty. I thought any imperfections in a lens would be caught within 1 year, and that the chances of a lens failing after a year was very low. I was mistaken.A few weeks ago the lens malfunctioned with my 7D giving me an ERR 01 code (just as my kid finished a cross country race). I cleaned the contacts on lens and camera (about 3 times) per the user manual for an Err 01, but the error kept on occurring intermittently freezing the camera. Adding to the mystery, the lens works fine with my old XT. I have sent the lens into Canon's factory service per their direction and have been quoted $284 to repair it. It's unfortunate Canon don't stand by their products as Nikon does - especially their heralded, expensive quality "L" lenses!