Product review (4 stars): Good, but insulation would make it better.
It's great for what it is.  If it were insulated I would give it a 5 star rating.  Think about it.  The hole that a dryer vent requires is still a big thermal bridge from outside to in or vice versa, even if the hole is covered.  It wouldn't take that much to insulate it.  Everthing exposed to the outside could be enclosed in foam insulation, including the floating valve cover.