Here's a quick gallery of images shot in a parking lot area just to give you an idea of the range this Canon 100-400mm F/4.5-5.6 has. Everything is hand held with IS on, from a Canon 5D Mark II. These are the JPEG's not the raw, no post processing except for resizing the image for web. I possibly even had my sharpness turned down for video mode on the profile, but you can see it's a pretty sharp lens zoomed in or zoomed out. You'll find related images when i'm zoomed out and zoomed into an object standing at the same spot. More video samples will follow soon..
Canon Zoom Telephoto EF 100-400mm f/4.5-5.6L IS (Image Stabilizer) USM Autofocus Lens
I own the 100-400, and its a great lens. I used it with a 2x adapter and movie crop mode on my t2i for an effective 5,600mm (I think), to shoot some video of the moon.
I bought my 100-400MM for shooting wildlife and I must say Im very happy with the quality and sharpness in this lens. for wildlife you cant go wrong with this lens.
Curious to see what sharpness level you shoot at for stills..I shoot one click from the bottom on video.