The Canon EF-S 10-22mm is an excellent ultrawide lens! I consider it the best one available for Canon APS-C cameras.
It's sharp and well corrected. It's also unusually resistant to flare (which often can be an issue with ultrawides, since they cover such an expansive angle of view.) It's the best of the ultrawides in controlling flare.
Build quality is "Canon midgrade/USM". Well above "kit" lenses, but not L-series. Of course, it's not priced like an L-series, either.
I highly recommend getting the separately sold, matching lens hood for it. it's a bit large, but works well to protect the lens.
The only minor niggles I'd have with the 10-22mm are the large hood (a bit of a pain to store in many camera bags), and the variable aperture (f3.5-f5.6). But the aperture really isn't an issue out in the field. It might be a minor issue if using the lens with manual flash, but it's unlikely I'll be using this focal length in studio anyway. Big apertures aren't really needed by most people on an ultrawide (we are usually stopping down for more depth of field anyway), still I'd prefer an f4 lens if it didn't effect other things. The variable aperture likely helps keep the lens a reasonable size and weight, as well as more affordable. It also might make for a better corrected optical formula and the extra resistance to flare I noted.
Unfortunately, I don't have any sample images online yet because I only just added a 10-22mm to my kit (I've been using a Tokina 12-24mm for some years, which I consider the 2nd best ultrawide... though the Tokina 11-16/2.8 is close, too). You really wouldn't be able to fully appreciate the image quality at Internet resolutions, anyway.
From all I've seen using it so far, and some limited experience with the lens before getting one myself, I wouldn't hesitate to recommend the 10-22mm. Get it, you'll enjoy it!
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Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
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