based on the fact that far cry ran much slower at e3 with the 3.0 patch.
Ran much slower than what
? Like you are in a position to say, not even having any first hand experience with how the SM 3.0 add-on compares to the SM 2.0 version.
Crytek themselves state that the add-on uses SM 3.0 technology to primarily improve performance vs SM 2.0. Logically, there would be no good reason to include an add-on if it was not worthwhile to do so.