I've also been looking at this lens (24mm f/1.4L II) and considering it for my next purchase, but it's a hefty chunk of change. I've tried it out a couple of times in a photo store, and loved it.
A wide angle, wide aperture lens with top notch optics is what I'm looking for. I love the 50mm (which I already have), but I shoot with a 7D, so I'd like something a little wider for the crop sensor, and don't mind paying extra if it's that much better. The other option I'm looking at is the 16-35mm f/2.8L II, with a trade off of aperture for a zoom lens which is wider and longer.
Before anybody goes into the (much overstated) argument that I should go for the wider lens because of the crop body I'm using, let me make clear that optical quality is most important to me, followed by maximum aperture value, then followed by factors such as vignetting and CA. I'm more than happy to move my camera's position to the subject to compensate for differences in focal length, if it means using a better lens.
I have a feeling I wouldn't be disappointed in either one, but for the premium that these two lenses carry, I want to select the right one. Could anybody give any advice on why I should or shouldn't make one of these two lenses my next? Anyone who has experience with both and could recommend one over the other?