Product review (5 stars): Half of a dead lizard...
This is an excellent and easy to use product.  The whole process from taking parts out of the box to cleaning everything and packing it back took me 30-40 minutes with the cleanup taking the longest.

I knew that 12' of flexible rods that come with the LintEater Dryer Vent Cleaning System would not be enough for my application, so I bought an extension pack from the local Lowe's that had the best price for LintEater extensions.  I used the total of six rods, which is 18' and I had about 1.5 foot from the drill to the vent and about 1 foot came out on the other side.

The manual says that you can clean the vent from the outside or from the inside.  I decided to go from the inside thinking that the brush would push loosened lint outside like it looks in the picture on the product page.  I used the supplied shop-vac attachment to minimize mess, and it worked well.  There was a little lint that the brush pushed to the outside, but there was about 2 gallons of lint in my 5 gallon shop-vac (<a data-hook="product-link-linked" class="a-link-normal" href="/Vacmaster-VWM510-Wall-Mount-Wet-Dry-Vacuum-Powered-by-Industrial-2-Stage-Motor-with-Remote-Control-5-Gallon-5-Peak-HP/dp/B001O6RA6Q/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">Vacmaster VWM510 Wall Mount Wet/Dry Vacuum Powered by Industrial 2-Stage Motor with Remote Control, 5 Gallon, 5 Peak HP</a>).  I also pulled a half of a lizard from the vent, but I could not find the second half even after running the system through the vent one more time time.

The manual suggests using a cordless drill with a clutch, I am sure to avoid damage to your duct, but my cordless drill's battery was dead, so I used a corded drill and it worked fine.  You must be sure that the drill is set to turn clockwise or the rods may disconnect inside the duct.

Everyone's project will be different, but I strongly suggest using a shop-vac to minimize the mess.  Lint looks solid when it is stuck inside the dryer vent, but it becomes very dusty when loosened.  I also found that although it is tempting to connect all rods from the start, it is not convenient to use the system with too many rods outside the vent because you end up standing with the drill too far from the vent and the rods create a slack and then twist together similar to how a twisted rope would twist together when you fold it in half.  I started with two rods and connected each next one when all but 5" of the system had disappeared in the vent.  Additionally, the shop-vac attachment is designed for a 2" hose, and the manual does not recommend using smaller diameter hoses to avoid clogs, but my shop-vac has 1 1/4" hose, so I used duct tape to seal the hose against the shop-vac attachment and the 21' hose did not get clogged.

Overall, this is a great product and, if you want to clean your dryer vent, I suggest you give it a try.