I refuse to play any MMOs based upon a level system (except for WWIIOl, but thats because at higher ranks I get access to other weapons/tanks but the earlier ones are still effective), as they drive me round the twist. As I tend to spend roughly 75% of my time in any given MMORPG actually RPing, I get annoyed that I have to level up to get kit that I want to use for RP. Its damned annoying, as I want to be immersed, not rinse, repeat everything constantly to get the chance to do it all again with a new button to press every 10 or so levels...
Sorry, am badly scarred from MMORPGs.
I enjoyed the dance video, but not a game I'd play myself.