Not much info at this time, but there is some leaking out, I will keep you informed. But for now here's what I know.

At least five new multiplayer levels, two new weapons (the Syringe and Machete) and some graphical improvements including 24 bit textures and better lighting and particle effects. There are also hints in the article that there might be support for user created gameplay modes in the Xbox Counter-Strike, although there were no specifics mentioned.

This was taken from the GameInformer magazine.