I got it a week and a half ago, but yesterday was my first real use. First, a disclaimer, I like push-pull zooms. I used them quite a bit on film cameras, and have no problems with them.
The lens is the 100-400 f/4.5-5.6 IS. I do have other L lenses, this is not my first. The build is typical L, there is no reason to take it easy on this lens.
My initial impression was that the autofocus was slow. I then switched the focus range switch to 6.5m-infinity and it was great! The focus snapped right into place. Faster than I anticipated.
The IS worked very well, and is actually quieter than some other IS lenses that I have used. I get the initial "clunk" as the IS engages, but can't hear it after that. I typically use a tripod, but yesterday I used a monopod plus IS. It is not a substitute for a tripod, but I was very pleased with the setup.
I found the tension ring handy. I kept it on loose when I was using the lens, but tightened it when carrying the rig to keep the lens from zooming.
This lens will be a great addition to my setup. Sorry there are no pictures - I do not have them on this computer. But I'll be posting some in the future.
-Ryan
