You know its funny you would mention custom materials and models. I actually just started learning XSI and creating custom textures. I think its kind of annoying to get the lighting and bump mapping right on textures. So far I have taken other reference textures from Valve and used their attributes on mine for practice. I plan for my next map (way in the future) to be all custom materials, and a few custom models.
BTW thanks for the honest opinions
Tycell: I would say de_Vostok would be another cool port from csXbox to Source. I dont think that will be my next map though.