The 24L is probably my favorite lens in my lineup. It was a lens I wanted for a long time. I had actually originally gotten the 35L (which is another FANTASTIC lens) and 24L to test against each other. I kept the 35L which was nice on my 1D Mark II and the PERFECT focal length on my 5D. When the 5D went, I wanted that focal length back and, based on ONE website, bought another 24L. On my 1D Mark III, it has quickly become my favorite.
It is the perfect wide-angle (good for full body shots and close ups of dogs) and super fast. It is a good size and very solid. The lens hood can be shared with my 16-35L. Since the Nikon D3 was released, I have thought about “going to the dark-side” but the inhibitive price to replace this lens with the Nikon 28mm f/1.4 has kept me from experimenting with the “other” brand.