I doubt FSX will support Physic Cards. And it also wouldn´t
make to much sense.. cause FSX doesn´t use
much of the the Physic features such a Card has to offer
(Ragdolls, Rigid Body Dynamics, Softbody Dynamics an so on)
The only case would be the touchdown
(wich allready works well) and crashes. But FSX is not a crash simulator !!!!
It could be a solution for flightmodels.. if the flightmodels would be based on real physics (like x-plane) and not config files (FS Series). But also in x-plane the flightmodel is not such a performance problem that it would benefit to much from a physic card.
Those cards are made for games with big explosion.. where parts needs to be scattered around and things like that.. but not for a Flightsim.

cheers,

Cant remeber where but I read that the PhysX stuff will end up being incoporated onto the actual graphics card, i.e. DX10 ones. If this is the case then I'd hold off buying one and wait to upgrade to a DX10 card with it on.

If what I read is not true (could well be) then if you play the games that support and use its features its worth it  8)