NV has shown they will take every opportunity to lock out features on competing hardware, never mind the end user. Batman, Hawx etc. are proof of this. And you chose to ignore one thing, there is NO technical reason that a person should not be allowed to run PhysX on a system with an AMD card. People do it all the time with hacks, what NV is doing is quite honestly anti competitive and probably violates anti trust laws. When you buy an Nvidia card one of the advertised features is PhysX, but I don't recall seeing anywhere on the box that says I can only use it in the absence of an AMD video card.
And now you're saying PhysX is only for modest enhancements? I thought PhysX is supposed to be revolutionizing gaming, adding substantial and significant visuals. If PhysX only mildly enhances the game then why bother with hardware physics at all, just do it on the CPU, it has proven to be perfectly capable. Everyone gets the visuals, not half the market.
I thought you said you were a realist?