The Mac version of MC does not (yet) include all of the features of the Windows version. They are now being developed in parallel, and JRiver is working to back-port much of the functionality of the Windows version to the Mac. These features may become available in the future, though there is no current timeline that is fixed in stone (so, no promises, and big features like these will likely be in another future major version number).
However, the current version of MC Mac is limited in the following ways:
* Audio only
* Does not have Theater View
* Does not have Ripping
* Does not have Handheld conversion and sync
It does have:
* Access to the full audio playback engine for Media Center (including the DSP, DSD, adaptive volume, and all the other goodness in there)
* Full compatibility with MC's Media Network functionality (including using/serving Libraries to clients running on different OSes).
* Zones
* Users