Sharp, great IQ, fun to use with really interesting possibilities!
Huge front element with no screw on filter is a bit frightening...
I've had this lens for about a year now, been using it on both my rebel XT and an old canon film SLR. On the XT (1.6x crop factor), the fisheye effect is barely noticeable, and its served as a great workhorse wide angle lens. Quality really is impressive for the price. On FF, the lens is downright dizzying. The results can be a bit gimmicky, but when used tastefully can produce some really incredible images.