12 is a good lens, you paint it too shabby IMHO.
Not my intent, sorry...the 10-22mm is a great lens, IMO. Do note that I called out distortion specifically, that's notoriously difficult to control in a FF ultrawide lens, and much easier to control with the smaller elements used in an EF-S lens.
The EF-S 17-55mm, 15-85mm, and 10-22mm lenses all deliver optical performance that is on par with many L-series lenses, and in fact, those lenses all outperform 'sort of equivalent' L-series lenses when comparing both on the same APS-C camera (e.g. the 17-55mm is better than the 16-35L II and 24-105L when comparing all of them on a 7D - and I know this from both test charts and personal experience). But when you put a different camera into the equation, and compare an EF-S lens on APS-C to an L-series lens on a recent FF/APS-H body, the larger sensor confers some IQ advantages. So, for example, the 16-35L II on a 5DII will deliver better overall performance (although barrel distortion is definitely worse) than the equivalent framing of the 10-22 on a 7D (again, from both charts and my own real-world experience having used both combos). The IQ of the 10-22mm in the 7D is already very good, it's just that the 16-35 + FF is slightly better.
You can see an aspect of that in the real world (sort of) with people who've popped off the rubber piece on the 10-22's lens mount and used it on a 1DIV - the 10-22 delivers images on the APS-H that are better than those from an APS-C body.