owned one for four months now have nothing bad to say about the lens itself. it's just great.
the price for lack of a tripod ring is a little steep but given what's happening with all new Canon lenses it's not out of step.
the zoom ring and manual focus ring are in different positions than a lot of lenses but after using it enough where zooming is instinctive i like the position better because the camera is more balanced in my hands.
no Canon extenders but is compatible with the Kenko. i guess results vary because i have the $130 Kenko 1.4x extender on it and even though it's reporting f/8.0 to my 60D it still autofocuses.
which kenko? I have heard the older DG versions will AF its the newer DGX ones that are suposed to not AF
when i used my DGX one on my 1Dmk3 with the 28-300 L it would even AF using outer points at f8 not only the center point but they were noticably slower so i primarily used the center point. I dont own any 5.6 lenses anymore to test this out on tough