Product review (5 stars): Works like a champ on the dryer vent, not so well on the gutter
My wife noticed the drying time taking longer and longer, almost to the point of us kicking the 2-year-old Whirlpool Duet out to the curb.  She found this product via a Google search for sources of long drying times.  I read the several positive comments and thought it made sense that our vent may be clogged with lint.  I had the 15+ foot dryer vent cleaned in less than an hour, including cleaning from the roof (vertical run from the dryer to roof) access and from the garage connection next to the dryer itself.  After the cleaning, I swept up a decent pile of lint, just as others had reported.  We are both surprised how much better the dryer now works.  Drying time was reduced from about 2 hours down to 45 minutes for the toughest-to-dry clothes.  I really recommend that you try this before calling the service technician out to tell you that the dryer works fine.

The cleaning system also says it can clean gutter drain spouts.  I tried using the flex rods and the special blade attachment provided in the box.  It worked pretty well but caught itself on some tight turns and bends.  Those rods are not very forgiving if you get them extra twisted, especially on a powerful cordless drill.  I didn't have any problems when cleaning the dryer vent with the larger diameter metal tubing.  I think this product is best used for the dryer vents as it was designed; make sure you use good common sense and wear your eye protection and keep the drill torque/speeds on the low side.