We've had this bed in the house for several months now.  My old man Lab refuses to use it, even if I pile on fleece blankets.  He's a combo belly sleeper and back sleeper.   I also have a Golden Retriever (Belly/side sleeper) and she has no interest in it either.  I have moved it to various locations in the house, but they always opt for other beds.  I wonder if the sides are not high enough to create a sort of enclosed feel to the bed.  Who knows why, but it's just not a hit with these two.