I recently bought two of these beds for our boxers - both dogs are over 65 lbs. and I ordered the MEDIUM.  Glad I had read the reviews because they do run large and the medium fits both dogs with plenty of room to spare!  They were very fluffy and full when I took them out of the box but them seem to be flattening now after a few weeks.  Hoping they don't become too flat which is why I'm only giving 4 stars.  Dogs took to them right away!  

Pros: Oversized and good quality fabric
Cons: Seem to flatten quickly