Product review (5 stars): Buy it, it works!
I have had this product for MANY MANY years.  I actually bought it off of Sky Mall, that will tell you how long.  I have a very long vent run with 3 90 degree turns so I had to buy the extension kit too.
When I first bought the LintEater, the dryer vent was so bad it would take over 2 hours to dry a load of towels. After cleaning it took about 45 minutes.
I typically clean the vent in the spring and fall to keep it running optimally.  I can usually knock it out in about 15 minutes.