Of course PhysX is great (at least in theory, I'm not a programmer).
But in its current state it is in no way an argument to get an Nvidia card, simply because there are almost no games that use it (thanks to Rollo for the backup on that) and most of the ones that do are crap.
Also, the problem is that in the games that use it, the stunning effects that result from it can as well be faked, which doesn't look as good (call it preprogrammed or static) but is hardly noticeable by a "normal" customer. The difference would be subtle. The Nvidia promo video simply didn't show any effects at all, this is of course a drastic difference. Games like Half-Life 2 are good examples of how cheap fake effects can come close to much more sophisticated algorithms. Everybody can see the difference between a scene with and without HDR at first glance. But this already gets harder with a simple bloom effect.
Plus it doesn't cost as much performance as PhysX does. My Core i7 920 / GTX 295 rig wasn't able to render Cryostasis with advanced physics enabled at what I'd call decent frame rates (also see here
. Another example here:
Instead of the water drops, there's nothing in the left scene. That's a design decision, not a reason to use PhysX. It's not like there wouldn't be an alternative. Or the bullet marks - nobody would ever notice this in normal gameplay if he's not an enthusiast looking for it so he can tell his fellows: look how great those sparks are!
GPU accelerated physics are a great thing: they make virtual worlds more realistic, they hopefully make it easy to design dynamic effects, they improve the overall game experience. And with the cards now being faster than any existing game requires, there's a lot of horsepower left to compute them.
But they're for sure not a reason to stick with a brand that tries to push a proprietary technology. Nvidia can make the people think that this is the case though - that's what makes them so dominant. So this would probably be more precise:
Originally Posted by Rollo
The reason ATi never gains any market share is they have no money to offer the public the features Nvidia makes the public think it wants.