Thanks for the quick reply. I'm not sure if we are talking about the same type of screen, but we might be.
I've seen the screen that fits in the gutter at the top of the downspout, and those things get clogged real fast and cause the gutters to overflow.
The screen I'm talking about is flat and lays across the whole top of the gutter in three foot sections. Is that the kind you have seen get clogged? I guess it could get clogged up if no one ever brushes the leaves off. I'm hoping that I can blow the leaves off the top of the screen a few times a year with a leafblower or shop vac attachment that lets me do it from the ground instead of climbing a ladder and scooping the leaves out of a second story gutter.
Maybe it's like a lot of things -- sounds good but it doesn't work!