Very comfortable. I have 100lb rottie mix. It is definitely big enough for him and hold his weight. 
This is his first dog bed even though he is 5 years old - I thought he was mature enough to have a real bed. But unfortunately because he smells the foam and thinks it’s a big toy to destroy. The first time I left him unsupervised with it he immediately tried to tear it up. I got back in time to save the bed. For 100 I was mad at him and I don’t think he can be trusted. Technically I can’t return it for that reason is my fault, but I will be donating it to my local dog rescue shelter for a dog who will not destroy this! Back to blankets for my dog. Lol.