I've had this product for one day.
I sit with a window behind me. When I have the anti-glare screen on, I can see the reflection from the windows; when I have it off, I don't. So that's bothersome.
This filter is too small for my monitor. I have a 18" LCD, and it fits just barely so I can't see the edges of my monitor, which is annoying because my toolbar is at the bottom and I can only see half of it. Whatever anti-glare screen you buy, I recommend going one size up so you don't have this effect. (It'll look ugly, but it'll work.)
Also, the ground cable is conveniently located right where my power button for the monitor is. This means, if I touch or slightly adjust the screen, my monitor turns off.