Product review (5 stars): time saver
This is a great product that cleaned 20 feet of dryer vent with ease (with the extension package).
It has shaved 30 minutes off of our dryer's drying time.
I used it with a leaf blower for added drama, and it was powerful enough to spit out a piece of a brick into our back yard.  Lord knows how the brick got into the dryer duct.
Instructions recommend doing it more than once a year, which seems like a bit much, but I'll definitely do it annually.