I bought mine used for $125, it was a real bargain. I liked it so much that I sold my 17-40L.
While its not perfect, it is a excellent lens and there are not a whole lot of 17mm FF prime lenses for Canon. I'm not much of a wide angle photographer, but it works for me. This is a snap shot I took shortly after buying the lens.
It was taken with my 5D MK II at ISO 100, f/16, 1/60 sec.