The gutter traps I tried go into the top of the downspout with the intent of keeping leaves out of the downspout. However, they don't keep leaves from backing up against the gutter trap and clogging the gutter anyway.
I've had great luck with a gutter guard called Gutterbrush. They only sell online so you don't have to have a high pressure salesman at your house and it's cheap.
I've been using a pretty simple and inexpensive system for a couple of years from http://www.gutterbrush.com. It cost only $390 to protect all my gutters. It works very well for me. I haven't had a clog, overflow or have I had to climb the ladder in two years.
It's gotten pretty good reviews across the web. I think for as little as $48 it's worth a try. They say they'll give you your money back if it doesn't work for you. I figure it saved me close to $3k over the high-pressure sales cover options.
They have a video on the web site and they will sell you a really cheap trial pack to prove it works. They claim a lifetime guarantee. Check out the video at http://www.gutterbrush.com/how-gutter-guard-works.htm .
