Product review (3 stars): Worked for about three years.
When it works, it works well.  Drying time was cut in half.  Our exhaust distance is over twenty feet with two elbows. But bought this about three years ago.  The motor is not in the dryer vent flow but is not protected from external dust.  It was under the house and has another, separate cooling fan that pulled in dust from the surrounding area. Eventually, that dust built up in the motor and caused it to fail. They do not sell a replacement motor, and you have to purchase the entire fixture again.  Nothing wrong with the rest of the device... just the lousy motor.