Product review (5 stars): Awesome ..... Worth Every Penny
This is the best invention since sliced bread, I am not sure why this item is not more commonly available.

During Michigan Fall / Winter our laundry room would turn into a meat locker, The dryer into a mini sub-z freezer [ Seriously no kidding .... ]. Despite frequent cleaning, the flap of the existing vent  POS - Builder special  , would stay stuck open due to lint / snow drift, our heating bills  and electricity bills would soar thru the roof [ Our dryer is electric ].

I finally stopped procrastinating and purchased this unit, installing it took me approx 1 hour [ I am no Bob Vila ... ], the hardest part was removing the existing vent and the ton's of caulk surrounding it.

We noticed a huge difference in the temperature of the laundry immediately after installation ..., last night / this morning while the outside temperature hovered around freezing, our laundry room stayed warm and toasty.

It's too early to comment on the saving, but I am confident it would easily cover the cost of the unit and the installation time ....

I am so impressed with this product that I purchased 2 additional units to replace  other exhaust vents.

Alas, We miss our meat locker ...... :)

Update : Dec. 2011, We love this, Our laundry and laundry is warm and toasty, no more cold air seeping in !!

Update : Jan. 2014, Yesterday we had once of the coldest winters, -13 F with windchills way below -40, Our laundry room was warm and toasty no cold air seeping in, 5 stars for this product, the inventors and company has done a marvelous job with this awesome product.