The interest in EVR is mainly because of new nvdia drivers that supports 8500/8600 series with full H.264 hardware decoding but only in Vista with EVR (PurevideoHD).
Bye
http://www.nvidia.com/page/geforce8.html said:PureVideo HD support is currently only available on Microsoft Windows Vista for GeForce 8500 and 8600 graphics processors.
Until it is either back ported XP, or Vista has a much larger market share, I don't see it being added. But hey, who knows.