This is gonna put developers in a sticky position... I know a good few are very interested in the multi-thread capabilities in DX11 even if they aren't interested in the rest of the features (HINT: I'm not saying theres no value to the rest of the features) ... but they aren't gonna start implementing features that lock out 60+% of their market...
People are gonna derride me for saying it... but right now with the balance of GPU spread DX11 is no more or less gimmicky than physx is :S
Your comparison is really poor though.
DX11 is like PhysX at the moment in a sense, but it's not the same as a gimmick.
PhysX is a gimmick at the moment, no doubt, until hardware physics is widely supported, it's a gimmick tacked on to games, once it's widely supported, the gimmickyness of it will be gone, as they can implement physics into games that are an essential part of the game, until then, they're just visual features tacked on.
DX11 is new and upcoming, to call it a gimmick sounds uninformed.