I just got back from the vet. We had Cyrano, our big male, put down. His cancer had reached the point where it hurt him to put his foot on the ground and bothered him all of the time. The choice was leave him in pain, keep him drugged into insensability, or send him on his way.
I have never been around a sweeter dog. I've had some that were brighter, better watch dogs, more playful, or whatever, but none with a sweeter personality than this big guy.