Bad weather again, but here is an example of the 80mm setting.
Indoors, no flash and a realy difficult situation a Cat in a rather dark living room in front of the window.
Only the eyes have been a little enhanced in PS.
Overall I'm VERY happy with the lens, the OS is really amazing and very effective, I can shoot under 1/100 on 400mm and still get reasonable good shots, when I go to 1/200 on 400 they are really good, with my previous lens and with OS of you can really forget this.
The Focusspeed is very slow, that's true, but to be honest it's still fast enough for anything I do, on continues focus it can easily track birds and soccer players so that's no problem.
The manual focus is really amazing precise and quick.
The sound of the lens is maybe a problem for some wildlife shooters, but I think the 400mm reach will give you enough space between your subject, it's not a really noisy lens but it's a bit noisier than for example my 70-210 f2.8 APO from Sigma.
Overall I'm glad I choose the Sigma over the 100-400L from Canon.
I shoot ALOT on 400mm wide open and the quality is outstanding optical, even when stopped down two stops there is hardly any difference in sharpness, so my uneducated quess is the optical quality is good.
I can whole heartedly advice anyone the 80-400 OS.