While I agree with what you guys are saying, and I'm not doubting that he was a hard worker, I don't believe that he is underrated. Personally, and I mean this with no disrespect, Mason's drumming wasn't all that difficult as you guys mentioned. I'm not saying that you need to execute a million fills or else your a bad drummer, which Mason was not. But I on the other hand don't believe that he showed an amazingness to his drumming. His drumming never stood out, not that it had to, but then again you can't say that he's underrated when his drum compositions are rather straightforward. He wasn't revolutionizing the art of drumming in any way either. I love Pink Floyd, but in the end I can't call Mason an underrated drummer. Sure he's shown flashes. And I particularly love his performance on One Of These Days (especially the Pompeii version). But I don't think he's underrated. I don't think he personally compares to Keith Moon or John Bonham for that matter. But he didn't need to because of the style of music that the Floyd played (a much more subdued style than that of Bonham or Moon's bands). And I'm not saying he's a bad drummer either. I just don't believe he's underrated (because of the previously mentioned reasons).

Take a look at a drummer like Chris Adler. He's done so many interesting things on the drums.