CocosDenshion are based on Win32 MCI Media interface now.
It has a lot of weak points, low efficiency, doesn’t support sound mixer, only support two audio format(wav and midi), …
The reason for decided to implement CocosDenshion using MCI on win32 is it’s very simple to use(only cost one day on it).
By now, after upgrade cocos2d-x to 0.99.5, we have plans to improve the performance of ocos2d-x on win32 platform, but the priority lower than iphone android and uphone.
So, optimistic estimates, implementation that after two months.