Since Leopard, Apple have altered their theme setup to something that hackers have spent months trying to reverse-engineer, to little or no avail. This is most annoying, I would sure like to have my "Menu Enhancer" theme back.
The closest I ever managed to get was by hacking the resource files inside ~/Library and /System/Library/... the only thing I managed to get reenabled was a 2D - Vaguely similar dock (Just recolouring the 2D one included). I agree its a pain and totally sucks (Hence why I still am glad to use 10.3 and 10.4 regularly).