We had Gutter Helmets installed on our prior home, which was in a wooded area. We loved them; never had to clean our gutters in the 10 years we lived there -- prior to the install they needed constant cleaning. I believe there was a corner that wasn't draining correctly so they came out and made an adjustment. On another occasion our gutter was clogged and we had to have them back out and were told that a bird had made its way into the gutter and built a nest -- they removed the nest. The product came with a very good guarantee, so we never had to pay when they came back out since it was within the warranty period.
I will add that my mother had them and did not like them -- don't know if she had the Gutter Helmet or another brand. I'm not sure what the issues were, but I remember she always complained of the large icicles that formed in the winter, so I'm assuming the problems were with improper drainage.