Byrnie
Headphoneus Supremus
Something about it does make things sound a bit...off...but the sheer positional advantage is why I use it anyway.
It's like having an aural wallhack, as I always say, and the sound samples in most games aren't the best to begin with. Thus far, the only things I've found to even compete with CMSS-3D Headphone's positioning are Rapture3D's headphone mixing modes and Aureal A3D on a Vortex-chipset card set to headphone mode. (Remember when all those competitive Counter-Strike players insisted on AU8830 Vortex2-based cards for A3D support back in the WON days?)
But I'll be the first to admit, even with all my outspokenness on the subject, that it may not work as well for everyone. That applies to every headphone surround tech that uses a generic HRTF based on the human average, when every listener has a unique HRTF.
I never had a problem figuring out where someone was, by sound alone, with CMSS disabled. CMSS didn't have great effects on it and no professional CS players that I knew (including myself) used it but of course it's possible that some did.