Product review (5 stars): Fantastic product!
This product is phenomenal.  I was leery at the ability of the rod to make multiple 90 degree bends, but it did so without any problem.  I was amazed at the amount of lint that came out of the vent without using a drill attached to the rod.  Then when I did attach the drill, even more came out.  I finished by attaching a shop vac to the vent and I am pretty sure the entire vent, which is about 30' long, is as clean as it can be.

I didn't have any problem with it, but I was careful not to run  the drill too fast or torque the rod too much.  It would really be a problem if the rod broke or if the brush came off inside the vent.  Just to be on the safe side, I used duct tape on the joints and only turned the rod clock-wise so none of the joints could unscrew.