I never liked NVIDIA's way of using proprietary stuff. Even on Android they help developers create games for Tegra and just lock them to it. There's a new game released with Tegra 4 optimisations, but it only runs on Tegra 3 or 4. I have a Nexus 7 with Tegra 3, but I'm not going to buy a game that's locked to the hardware.
That's where I think NVIDIA fails, it limits things too much. With PhysX, if it even let me use a second card for it I probably would have, but instead it did its best to lock out the possibility. That's why PhysX will never make it. I'm sure a lot of people wouldn't have minded spending $50 on a PhysX card even if they bought AMD.