If nothing else, he's been an effective popularizer of science. A Brief History of Time has been a tremendous success, and it's served as inspiration for many of today's scientists while teaching the public a bit about how the world works. Pretty cool.
Saying he has "a disability" is a massive understatement. The man's body has been effectively useless for decades now, serving only to keep his brain ticking and providing a cumbersome and exhausting means to slowly communicate. But he continues to engage the public and maintain a sense of humor. So that's something.
Sure, he's a celebrity. But he's also done some great things even if you discount all of his scientific accomplishments. He's served well as the face and (robo-)voice of science for a while. I think he's worthy of a short jaunt up to space.