Today marks the release of RAGE for OS X, as RAGE: Campaign Edition is now available via digital distribution from the Mac App Store, Application Systems London, and GameAgent. Also, though the OS X edition does not seem to be offered on Steam, there is a new automatic patch for the Windows edition on Steam, among other things, adding a new texture detail option. Here's word on that:

Texture Detail: Enabling Texture Detail will improve up-close texture quality by performing upsampling with adaptive sharpening. This does not update or increase the resolution of the base textures included with the game but improves the perceived resolution and crispness of textures. This is an intensive operation and is only recommended if you have a quad-core CPU or higher. Please disable this feature if you encounter poor performance, stability issues or are given a notification that the game has run out of memory after loading a map. The Texture Detail option can be found in the Settings -> Video Menu.