Not trying to go too far afield, but in terms of sharpness only, how do people feel about the 200 f2.8 prime and the 70-200mm f4 IS. Are they as sharp as, or sharper than, the 70-200 f2.8 II IS?
The 70-200 II beats them both (although only slightly - detectable in tests, probably not relevant in real-world shooting).
Can I ask you your opinion about IS performance?
I have this lens and the f/4 IS version and I think that the f/4 has much better IS. Of course may be the weight of the f/2.8 lens is the culprit but I am not completely sure that it can explain everything. OK, IS definitely works (I can see the difference when I turn it off) and in fact it is very quiet.
But still I think that while the f/4 IS behaves like a true 4-stop version the f/2.8 behaves like it is not 4-stop but
1 or 1.5 stop only. Maybe it is just me but I am disappointed.
This shot was handheld at 95mm on a 5DII (free hand standing on a narrow bridge with no railing, not braced against anything), and was a 0.5 s exposure. Granted, there's a little motion blur at 100% viewing (but it looks decent at 1600 pixels - click the pic, then View All Sizes, then Original, check the writing on the wooden columns above the falls). That's
5.5 stops below the 1/focal length guideline - the IS seems pretty good to me...

EOS 5D Mark II, EF 70-200mm f/2.8
L IS II USM @ 95mm, 1/2 s, f/5.6, ISO 100