I strongly suggest taking heed to all these complaints. In short, I will inform everyone about the following pitfalls about this product after installing over many thousands of feet of gutters for Leafguard.
If you have very steep slope roofs, bad idea. If you have alot of roof height(length) from top of roof to fascia boards, also bad idea. Reason for water behind gutter is because of installer being to lazy for not putting gutter apron under roofing shingles to the top of gutter.(Leafguard #1 problem). Icycles WILL dam up in most circumstances,(Several reasons for this).
After awhile, because there is no support for bottom of gutter, and after a couple of winters of ice dams pulling open the face of water intake, debris, especially pine needles, whirly seeds, and the like, WILL begin to accumulate inside the trough.
Lastly if you have large valley areas (this is where one roof will overlap the other) too much water volume will overshoot the leafguard hood. My suggestion is get regular style gutters, pay to have them cleaned once or twice a year, and since I know the price differentials, you can live in the same house for twenty years and be about even.
Product or Service Mentioned: Leafguard Gutter.