I bought this lens to widen the views possible on my EOS 10D. The build quality is great. It feels like a little tank compared to the 50mm f/1.8. It's only sliiightly larger but nicely heavier than that lens. But, check the weaknesses....
Depth of field is great; The horribly wrong autofocusing is quick, and f/2.8 ain't bad either; Build quality is great; It feels like you could throw it at someone, hurt them, and pick it up and use it again
Here's the main problem: It brutally overexposes everything on my 10D; It's not reliably "x stops off" of you would simply set some exposure compensation whenever you mount it on your camera; It's very hit and miss.