Product review (5 stars): Excellent product, works as advertised
I have about 20 feet of dryer vent running from my downstairs laundry room out to the opening underneath my front porch.  I could tell there was no way to try and replace it, and my laundry was taking longer and longer to dry, which was a sign that it's probably getting clogged up with lint.  I found this item on Amazon and decided to give it a try.

The product works absolutely great.  Having a shop vac is a must though.  There is an attachment that you put on one end of your vent (usually the inside access) and plug your shop vac into it (fits perfectly snug).  Then on the other end of the vent, you insert the cleaning want attached to a standard drill, and continue to add attachments as needed.  The brush attachment scrubs the inside of the vent and the shop vac sucks out all the lose lint.  After cleaning my vent, I was curious how much lint I had removed, so I cut open my 16 gallon shop vac bag and found it about 1/2 full!  Glad I did this sooner than later!