This is one spectacular lens. This is one of the two L primes I own and have ever tried, the other being the 135mm f/2. The 135mm has the edge in image quality in that there is less chromatic aberration wide open, but this lens gets more use because of the focal length. It really is a wonderful perspective on full frame, but also on the 1.3x sensor. It is a wide angle perspective but has just enough reach to make for interesting portraits/group portraits. Having extensively used the 50mm f/1.4, the biggest difference has to be the contrast and colors, with the 24mm being so much more saturated so that the images straight from camera require very little processing. The L brand really speaks out in this regard.
I believe this lens is way underrated due to the more popular 35mm f/1.4 To be honest, I was looking for the 35mm and hadn't considered the 24mm until a deal came up. Needless to say my desire for the 35 has dissipated; I am completely hooked on this lens.
If you are looking for a fast prime on the wider end, you won't be disappointed with this lens.