My better half swears by his, though I have doctored it by removing the plastic lens and the little metal frame. This means that you have the increased distance from the camera (Cleaner screen) without the reduction in the viewfinder size. It's perfect for him as he wears varifocal lenses and finds that with the normal eyepiece he can't get his glasses in the right place to get all the info in the viewfinder in focus.
Tara
Doh, too late!