Originally posted by StealthHawk
so does that mean vertex shaders are used? because that answer really isn't clear. i thought i remember hearing Sweeney say that VS would not be used, and that PS would be used very lightly, in accordance to what you said. i only know that they will be used for water effects for sure.
Most likely it means this: Vertex shaders were not part of the design, but hardware with them can be used to make a particular effect more efficient. One problem with fixed function shaders is that they don't know what the programmer was actually trying to achieve and often do more work than necessary, for example when a texture is scrolled across a polygon such as in a water effect, the fixed function shader may do a full 4x4 matrix multiply to calculate new texture coordinates, but a hand coded shader can simply do something like v = v + moveValue saving a few clocks per vertex.
So in summary, I think those with the hardware will get even greater performance, but those without will still get identical looking results.