As a landscape guy, I've always loved super-wide angles. I'm about to pull the trigger on either the Sigma 10-20, the Tokina 11-18 or the Tokina 12-24 (can't really afford the Nikkor 12-24), but I'm seeing a bunch of conflicting test results and user reviews. At this point, I'm leaning toward the Sigma, but I wondered if other members had experience with these lenses and some observations.

Thanks!