Late but definite answer
OK, four years later, but I do want to register the answer to this question for future reference:
I have tried the Sennheiser 333D on a MacBook running Lion.
The headphone works, but only in stereo modus, no 7.1 or 5.1 surround sound or DTS support. The options are simply disabled in your midi / audio configuration.
So, if you are considering this headset for a mac, it really does not make any sense, since 3D is kind of the main feature of the gadget (on a windows PC it works great, by the way!).
As for newer versions of MacOS - Sennheiser does not offer any drivers and is very vague about MacOS support, so although I did not try it, I pretty might would expect the same result.