I have since sold that house, but in the year after which I had them installed, I had NO problems with leaf, oak bloom, etc. build up in my gutters. I did not get the expensive kind (can't remember the brand, maybe Rain Guard) because I knew I would be selling the house. Mine consisted of a wire grid which fit into the gutter. Installed by Gutterman (national company). They showed me all of the options before I had the work done. (I also replaced all my gutters at the same time.)

They work great on big leaves.

Very small leaves, such as pine needles, can be a problem for some of the designs - bigger holes let them fall in.

whether people posting such opinions are people who have gutter cleaning businesses.

we get a ton of leaves and acorns. I'm pretty sure husband installed these because they are less expensive than other options.

A very different approach to gutter guarding. These are made from some UV protected open cell foam. They fit inside the gutter and keep pretty much everything out. Water has a free and open channel to run thru and the foam allows roof runoff to enter the gutter freely.

We had a big problem from a nearby maple that clogged our front gutters every fall. Since installing these (5 years ago??) we have had no problems whatsoever.

...that had their own drain to a storm drain or otherwise away from the house.

I would have a diverter over the entry doors to move the water off to the side.

the oak 'strings', I call the stuff that falls in early spring when the tree is blooming, STILL get caught on top of the screens. I still have to go up and sweep/brush the string away else when it DOES rain, the water runs OVER the screens.