I just got finished watching Beater's Legacy videos and they made me curious. Specifically, the B4nny Legacy video with his scout play juxtaposed with his old demo frags made me recall how worried everyone was when b4nny switched to scout. I remember a video(fully charged?) where platinum was doubtful that the switch would work because b4nny's influence on the match would be lessened. However, b4nny seemed to be just as game changing and formidable as ever. The same thing could be said of when platinum played switched to demo and when enigma played roamer.
Comp TF2 is a game that allows for a lot of nuance in play style. Obviously good coordination and DM ability can get you pretty far, but there are some intangibles that make a player/team go from being good to great. What are the subtle things high level players do that lower level players don't? What are the things that good DM ability and team play don't quite cover? What are the things that make you think a player is good at tf2 rather than good at their class? What makes brilliant play brilliant?
Edit: To be clear, I'm not looking for tips to improve my play. I love comp. tf2, but i basically never play it. I just wanted to hear some thoughts/discussion on what makes a good player/team become great. There are some great comments so far with thoughtful answers. I'm really glad that I bothered to post.