Product review (3 stars): It works.
It took a little finagling to get it to fit into the tight space we have, but it's working okay.  I did what others suggested and put pantyhose over the end for extra filtering of the lint that could escape.  A lot of the air still goes outside because of the flap inside the unit, but enough comes in to heat our tiny laundry room.  If we were trying to heat a larger area I'd consider somehow closing off the flap inside so all the air stayed in the house.  Even still, this does push a lot of humidity into the room, so if you have a small room like we do (~6x7), you have to ventilate it so your walls don't get covered in moisture.  I haven't tried turning the flap to "summer" mode to push all the hot air outside yet, so we'll see how that goes later.