I was just thinking about my horrible experience with my Leaf Guard gutters and realized that the only way I would get over it was to let others know, so you can think about this before making a decision. This is a little vindictive, but when the company could not resolve my issues, they said in the politest way, that's fine if you don't want to pay the last $1000, we'll just "ruin your credit". That scared me enough to pay, but I'm still mad.
Do the gutters work is probably your main question. The answer is two-fold. I have a dutch colonial (so a very steep roof with an overhang) and also a couple of sections of flat and fairly flat roof. The way that leaf guard attached the gutters to my flat roof was with tape and glue. I live in Minnesota. The first rain/freeze, the tape glue came undone, and I had to wait until the Spring for them to fix it. In the mean time the rain/snow melt dripped between the gutter and the roof. Their comment, it should be fine, your roof was in good shape.
The installers just replaced what was there, but they made some miscalculations, so the drain spout for the side of my house ended right at the edge of my house, not too smart. They were good about coming and moving it, but I felt they should have figured it out before. The problem is that when they do drain, they wash away my back yard, noone mentioned that, and they weren't willing to fix that. They also put the drain right in my walkway, they were too dumb to figure out that it should be a little shorter.
As far as the steep roof. The top part of the roof had no gutter, they never mentioned it may need one until I complained about the noise. The top part of the roof drains onto the top of the gutter so when it's raining I hear pinging all night long outside my bedroom window. Noone mentioned that possibility. Also, given my house, two gutters in the front would look silly.
It's been a year, the tape is coming off again, I didn't have to clean leaves out, but the edge of my white gutters is black, so I do need to clean them still.
I think the biggest problem is that I trusted the company knew what it was doing and that they would install the correct gutters for me. When I asked the guy that came to fix them (for about the third or fourth time) if they really work on a flat roof, he said they weren't the best option for a flat roof. Apparently, it's typical for them to come yearly and re-tape them, I don't think they're willing to return to my house.
Also, after I signed the original contract, the sales man told me he made a mistake of $300, and he'd offer to split it with me. They were horrible! So, the moral of the story is that you need to be a little more educated on where you want your gutters, don't let them make the decision for you. Also, don't have them installed on a flat roof, and if you live in the Midwest, avoid Midwest Leaf Guard.
I feel better already!