We have twin beds. DH is a big guy and when we had our king size waterbed, he would stretch out and I had a very small spot, less than a twin bed! So we sleep really good now, unless DH starts snoring!
Queen size, and it's shared by two adults, one cat and one kitten, when the cat (Roxy) let's the kitten (Molly), share! I don't often sleep stretched out in a straight line, usually all crooked around the kitties!