I purchased a 12.1 in sheet because it was the same price as a smaller size and I can use the extra for something else. I didn't really care much for the anti-glare feature...i wanted a screen protector and a smooth touch surface.
Here are some pictures of the anti-glare. For $11 shipped...it's not bad, comes with a free microfiber cloth and it was shipped with a heavy duty cardboard insert to prevent bending.
http://photodon.com/lcdprotect-sheet.htm
The pictures seems like there is a difference in anti-glare, but I don't really know if it's a "real" difference or not