If you're asking these questions in such a general manner, I would suggest going back and understanding:
(1) what a real time kernel actually is,
(2) what parts of Linux this real time kernel patch set actually provides, and how it would affect your requirements.
It simply sounds as if you want a real time kernel for the sake of having a real time kernel. The simple truths are that:
(1) hard real time kernels are not possible in linux proper itself (there are too many code paths with variable execution times in the critical sections)
(2) therefore, hard real time patches imply a microkernel atop the linux proper which has its own API and executes at a higher priority than the linux kernel proper.
Do you have something which requires real time operation? LinuxMCE will not "magically" work with this kernel as is.
If you do, then of course you can use their API calls (i.e. in listening threads etc.), to make sure certain things always get done on time.
Sorry to deflate your bubble there,