Conclusion: I've always shot with prime lenses but I really needed something versatile and purchased this lens. I'm very satisfied with the performance and picture quality that I get as this is mounted to my 5D Mark 3. As for the price, I think it's way too expensive especially considering that the closure is made of plastic unlike the first versions which is made of metal.
Conclusion: Photography has been my hobby for over 20 years. I am not a pro. In order to evaluate a new lens, I shoot everyday life instead of brick walls. This lens is sharp wide open at F2.8. You do not need to stop it down to increase sharpness. This is what I love about this lens. It is like having several prime lenses in one package. I used the 35L and 50mm F1.4 for several years. They are good lenses. But I had to stop them down from F1.4 to F2.0 or F2.8 to get sharp images.
Pros: Fast auto-focus, Superior build quality, Super-sharp images