Product review (4 stars): There is that sweater she lost!
But I want my cake and eat it too.  The shafts are so flexible that if you're not careful, you'll experience what I did...one of the sections twisted up on itself and hasn't been the same since.  Therefore, I recommend a) a second set of hands and b) a little cautious discipline to make sure that your angle of approach will allow the torque to travel down the system, not just twist up the closest section.

It worked great for the ducts in the house that I am renting.  The brush was very gentle, even on the accordion section (which I removed and cleaned outside).  The smaller/longer brush was basically worthless for the model of dryer that I was cleaning.  But the system was overall quite effective for the vent ducting.  It was so much fun to look up in the hole and see clear through to the other side with nothing in between.  I recommend this, especially if you are working with non-linear ducting.  For straight ducting, you may want to find something with more rigid rod sections.