GutterStuff is a highly porous foam-y, sponge-y sort of insert that you pop into your gutter. It's supposed to keep out leaves and such while letting water flow right through.
Does GutterStuff really work? Yep! I've had it in my front gutter for six months now and it works just fine. So much so, that I just installed it in the back gutter as well.
Water flows right through this stuff. No matter how heavy a rain you get, GutterStuff isn't going to cause your gutters to overflow. Leaves and twigs, on the other hand, just sit on top of the GutterStuff inserts. Most of the flow right off with the rain, a few might hand on and have to dry out in the sun before they blow or wash off. Some do get caught in the tiny spaces between GutterStuff and the edge of the gutter, but not so many that it's any sort of problem.
I don't have pine trees near my house, but I've heard that GutterStuff works well with pine needles too.
Installation is easy, or at least as easy as anything involving gutters and ladders ever is (and that's a particular challenge in my house, with my sloping grounds and shrubbery in all the places the ladder wants to be). Once you have access to the gutters, clean them out (yuck!) and just put the GutterStuff inserts in place, making sure they're all facing the same direction (GutterStuff is cut at an angle and leaves an open channel in your gutter for water to flow).
The stuff ain't exactly cheap. Expect to pay anywhere from $2-4 a foot, depending on how much you buy, whether there's shipping, etc. A 30-ft gutter can run you $75. But if it means not have to go up and down and up and down and up and down....you know what I mean....and deal with gunky gutter-cleaning, then in my book, it's worth it.
By the way, I used to have screens over my gutters, a much cheaper options. They worked well for a while, but eventually collapsed and had to be replaced. Give me the spongey stuff, any day.
Need more information? Newspaper archives are one of the best online research tools.
If you're searching for information on people, try Intelius.