If the game does, does it look any better with or without?
p.s. I think FSX would look better with Nvidia Physx.
What would we do with Nvidia Physix in SSM? Don't be misled by the name: it does not do any Notable "physics" beyond collision, on a large scale. It can improve performance for games with a lot of particles which need to behave (or seem to behave) physically correct, such as showing an explosion and something being ripped apart as a result, in thousands of pieces.
We don't need to use a technology simply because it's there. It must provide a seriously compelling value to be considered.
/Admin
PhysX could be used for launch, smoke at landing, entry, and RMS firing in space, but that's about it. Would all the trouble be really worth it ? Not really sure, so I would go +1 with Admin there.