Product review (5 stars): Does a better job than a professional and is very cost effective.
This is an excellent product.  When I moved into this house I paid a professional to clear out our vents but it didn't work...dryer still took forever to dry something.  Made him come back and he removed a ton more and it was OK for a while.  Amazingly all he did was hook up a leaf blower to the inside and then go to the outside and fish around a little.  Not very effective as my dryer is like 20' from the outside...much farther than his tools reached.

I bought this product so I wouldn't have to pay someone and so I could do a better job.  Mission accomplished on both counts.  Steps:

1. Disconnect dryer
2. Connect this to a drill and feed it up in for a few feet as you run it
3. Pull out.  Then put a leaf blower in there and duck tape it.  Start the leaf blower
4. Go outside and drill from the outiside.
5. Keep inserting more and more until you get to where you drilled from the inside.  Drill in and then pull out (while still drilling)

Repeat a few times until no more stuff blows out.  You and all the area around your vent will be completely covered in lint.  But your vent will be clear.  Very effective and easy to use, even at a long length (I had two set of extenders in use in addition to what comes in this set).

The only thing to watch out for is having too much slack outside the pipe.  it can start getting twisted around.  You really do need to insert these one at a time.  Takes a few minutes, but does a great job.

I'm 100% satisfied.  I'm sure there are pros who use this tool or something like it, but the vent guy I called did a much poorer job than I was able to do with this.