Aressem wrote in post #17253822
Money is no concern. I want the best at 10mm. The 10-18mm is a fantastic lens at it's price-point, but certainly not the best. I appreciate your input though.

As I said, there is an extremely limited selection of lenses at that focal length, and none of them are L lenses or particularly super sharp throughout the frame. As mentioned, some are better at the center and some are better at the corners. Unfortunately there is no REALLY GOOD 10mm lens. There are offerings from Sigma (8-16 and 10-20), Canon EF-S (10-22 and 10-18) as well as Tokina (11-16), but all of them are very similar in sharpness. In fact they are often reviewed together and compared to each other. The general consensus is that the Tokina is best for low light stuff (f/2.8 aperture), while the 10-18 is the "go to" lens if you don't need low light.
As for sharpness, I personally find the 10-22 soft especially at the edges, though many people don't agree. Might be just a bad specimen that I used. However the Image Quality pages at the-digital-picture.com confirm my feelings. The 10-18 is the best in my opinion, at any price point (with AF). Sigma 8-16 is very similar at 10mm but costs much more.