I needed a factotum lens when I switched me to a 7D and this fell into the basket quite quickly.
+ Build quality (Can build houses with it)
+ Minimal distortion (do not know how it is on full-frame)
+ Red ring (hawt)
- Need filters for full weather tightness
- The lens hood that comes with will do no good on APS-C sensor cameras.
This lens is world class. On my 7d does it really well as a standard lens but basically it's a wide angle. The only negative thing is caring about the brightness, but it would be 2.8, it would cost double (at least). Can not live with 4.0, you should not buy this otherwise there are only good things to say about this lens.