Here is the reality:
1 - This is a marketing play by a company that does not have the fastest product on the market. Argue all you want on the future, but at the present, they don't.
2 - There will be some titles that are enhanced for Nvidia simply by using PS 2.0+ shaders. The developer may even be prohibited from trying to implement the same shader in PS 2.0 with multipass.
3 - Any REAL PS 2.0+ shader will suffer from performance issues. By 2.0+, I mean longer than 65 (whatever the PS 2.0 limit)instructions. Of course, this is all dependant on how many pixels are being run through the shader, but in general, this will adversely affect performance.
4 - Rest assured developers will not be using Nvidia hardware exclusively. They get ATI products very easily and have ATI products in their QA labs.
5 - The ultimate issue will be how 'enhanced' the effects are that are Nvidia exclusive, how they perform (I assume less since they will be performing more instructions), and if it truly makes the game anymore enjoyable.
The only problem that I see if that the mainstream market people will think that this means they need Nvidia hardware to get the best experience in their EA games. And those are the same people that are going to be buying the slower NV3x-based boards, thus when running those 'enhanced effects', they will be slower and slower. Quite the experience I must say
This post is not to start a flame war, etc. It is simply my take on it and that is it.