is UWA a canon term?
and besides the fact that it has an extra 2mm on the wide end, any comments on the sharpness, speed in low light situations, ergonomics, etc..?
edit//
is that extra $120 worth it for 2mm?
Thats debateable because you can just take a couple of steps back. The reason I brought it up was b/c I wanted a lens that was a fixed f2.8 as well, but I also wanted a Ultra Wide Angle lens. But I came to realize that I'll use this lens much more often than a 11-16 f2.8.
Sharpness/ergonomics I can't say much as I haven't shot with it myself. As for speed in low light situations, at f2.8 I think its great and fast enough.