I uploaded Screenshots (1680x1050) illustrating the difference between High, Very High and Extreme. As you all know, this does not alter the pop-up/in effect (to a huge degree) but visually, a few things do change.
Look at the Models in the first screenshot of the coffee machine, the plant on the left, and the chair on the left. Even between Very High and Extreme will you find differences.
Another one that jumped my eye was the vanishing side-lights in the parking house.
Then on the 6th, you can also see the writing on some walls vanish, the texture finesse being different across all 3.
Anyhow, its uncompressed BMP - so all JPG nazi's can breath easy.
(And yes, imho, extreme is blurrier - The game is still good)
http:///www.insayne.net/Crysis2