Product review (5 stars): it is worth it since our house will be more comfortable (no drafts) and reduce heat and air-conditioned air escape
It has really cut down on the cold air coming into the house via the dryer vent and has eliminated a big draft in that section of the house.  The downside was that we had to have a professional remove the existing vent and install the Heartland 21000.  I think that had more to do with how the original vent was installed but still, it added to the cost of the project.  Ultimately, it is worth it since our house will be more comfortable (no drafts) and reduce heat and air-conditioned air escape.