Conclusion: I purchased this lens for shooting small black box theatre productions without a flash, and these venues are typically not well lighted. This worked wonderfully with my Rebel. When I upgraded to a 5D and a 5D MkII I found this lens to be lacking.
Pros: Fast auto-focus, Superior build quality, Super-sharp images
Summary: This last copy of the 24mm was the last straw. I kept getting soft images on all three copies...I tested the auto focus and it was off just as in the last two copies and required micro-adjustment. Even using manual focus produced less than great results for such an expensive lens.
Conclusion: I have wanted this lens for a long time and finally ordered it. I just received this lens today. I have taken about 100 photos using my 7D using various focus points. Only about one third of these did the auto focus work. It's getting returned.
Conclusion: Build quality is high as expected for this lens. However the focus is inconsistent and the lens has severe front focus around 1.8. I owned the mark I predecessor and loved it, so when it was stolen I immediately replaced it with this one.
Summary: I'm on my 3rd Canon 24mm f1.4 L version II, all have had focus issues. The 1st was crazy inconsistent. The 2nd had a huge front focus and was still somewhat inconsistent. The 3rd that I just received is also inconsistent.
Excerpt: This particular lens was "off" dramatically in terms of focus accuracy. This was particularly disappointing because it was to go on a European trip with me (it got sent back instead). I have several other L lenses and will consider this an anomaly unless the next one is the same.