Product review (5 stars): Worked perfectly -- glad I purchased
I just purchased a new dryer and was getting very angry because it was taking a long time to dry (literally hours). Assuming it was not the dryer, after much research, I came across this cleaning system and all I can say is what a difference!  I had the dryer vents cleaned professionally a few years ago for a cost of $100; and after using this tool I realized that they only cleaned half the vent.
I live in a 2 story with the dryer on the 2nd floor, which means that the vent goes in behind the wall, up through the attic and through the roof. Well, I did exactly what the professionals did, and that was go through the inside vent and up, and removed a lot of lint build-up, but the dryer was still not drying in less than an hour. I ended up on the roof, and cleaned the vent from the top down which removed the clog and the end result less than 30 minutes to dry most loads.
I followed the directions to the T, and had no problems. Everything worked perfectly and I'm extremely happy. The hardest part of this whole job (aside from getting onto the roof) was putting the foil vent back onto the dryer and the wall vent.

NOTES:
- Be sure to use the big tall brush first, and then the small, wider brush. I.e., you need to do 2 passes to really clean the vent.
- Make sure to use the drill; you cannot just use the brush and rods. The drill actually rotates the brush to break up the lint and allow it to fall.
- Maybe if I had purchased the extensions, I would not have had to go on the roof, but there's no way that I could clear the entire vent with the 4 rods (12 feet)
- If working on the inside of the house, it's important to wear a mask because all that lint and dust will come down.
- Follow the directions, and tape the rods after connecting together.