I agree...this lens has unfairly gained a bad rep...typically from those who have read the reviews and haven't used it. Or have tried it, but with a biased view and an unrealistic expectation of L-quality. The CA issue is true but is overblown and is easily corrected. Even wide open the center is sharp and gets sharper still stopped down just to f2 orf2.8.
As for corners, if one is fair, some softness is to be expected with wide angles and my 35L is soft in the corners! And 28mm is even wider and this lens is not even an L.
The build is better than the other consumer lenses, while not as heavy as say 24II or 35L, this lens will feel solid if you handle it...it doesn't feel cheap. Again, some expect it to be the L build without paying for the L.
Ironically, "mood wise", this lens comes into its own on full frame, corner issues notwithstanding. And you can't beat f1.8 at this wide a focal length.
Canon keeps this lens in production for a reason. In spite of all the armchair punditry, this lens is a steady seller and a good performer on FF and doubles as a normal lens on crop bodies.
Not perfect, but highly underrated.