Product review (5 stars): As good as it claims to be.
Comes with a booklet that tells the user SEVERAL ways to clean ducts.  If your duct is like mine (in a crawl space so it must account for beams and wires and pipes and my crawling around so it's long and has bends and slopes), you can choose your method without lots of trial and error (because they already tried them all).  Plus, the rods are exceptionally flexible so I had little trouble cleaning around those bends without disconnecting the ducting everywhere.  (That's the trial and error part their booklet helped me avoid.)

My advice - read the booklet first (yeah, I know - how complicated is duct cleaning?).  Their booklet makes it even easier.

A hint - If you have a crawl space with a duct like mine, carry your new duct tape and the brushes in a plastic bag so dirt and old tape don't stick to them while you are working or on your way out.  Carry a second bag to put the lint in so you don't have to handle it too much. Their booklet didn't mention that.