Absolutely nothing wrong with using physics with CPUs, nowadays with 8 threads or more going around in cheap rigs, it's a disgrace that most games don't even use 4 threads. That is wasted resources. Devs should add advanced physics in graphics options in games, essentially "enable if your cpu isn't stupid".
Let the GPU focus on whats its meant for, graphics. Even top single cards struggle at 1080p just for rendering, it's backwards thinking to put physics as an additional load on the GPU when the CPU is sitting around idle.
Isn't it great that games like BF3 scale with 6 cores and huge overclocks?? All future games should be like this and more.