Has anyone tried this viewfinder? I've had a heck of a time finding reviews for it online, but it seems like a really useful little tool. I posted a topic complaining about fine focusing, and perhaps a product like this may help.
Oh, using a Digital Rebel
I use this on my 10D and find it very useful in many situations. It has two magnifications of the viewfinder image, I almost never use the higher one, it seems to be too high. The device allows one to have the camera in positions that would be uncomfortable otherwise, both lower and higher.
I believe that I get much better manual focus when using it.