A few things to keep in mind, this is a MANUAL focus lens (so no autofocus), the hood is built in (so you can't remove it), and the front element is round so you can't use filters. I read that people actually used the Canon version on EF full frame bodies like the 5D and cut the hood off. I almost bought this lens but decided to go with the Sigma 10-20mm instead This allowed me to use ND filters for long exposure landscapes which I use quite often. That being said, good price for this new lens.
It's an 8mm fisheye. Pretty much panfocus, not much need for autofocus.