Product review (5 stars): I don't know why these aren't more popular . . .
My washer and dryer are in the garage, so it's great to be able to capture the dryer's wasted heat during the winter. Additionally, this helps add some humidity to the house, which tends to be dry because we live in the desert. The screen on the heat keeper catches any lint that escapes the dryer filter.
I installed mine in about 10 minutes
The only down side is that the garage smells a little like laundry soap and dryer sheets, but I suppose that could be a plus for most garages.