Product review (5 stars): Easy.  Does the job.
The instructions were easy to follow, each section easily attached and it was a breeze to insert into the duct using my power drill.  I heeded the warnings in other reviews not to reverse the drill and not run it excessively fast, which I think was great advice.  The whole project took less than 30 minutes including the time to move the dryer away from the wall and vacuum all around.  Very pleased.