yeah I watched that earlier but did not even think about posting it here. its pretty sad to the gtx660 dip into the 30s with some of the physx effects. that means even a gtx680 will likely stand no chance of staying above 60 fps the whole time on max settings and high physx.
and for those that just skim through the video, there will be 3 physx settings. low will be regular physx that all the platforms get. medium and high will be hardware accelerated so you will need an Nvidia gpu unless you want to brave running those hardware level effects on your cpu.
Well, one thing to note is that the demo is running the 660, not the 660ti.. so there is some performance to be had. I think a nicely overclocked 670 shouldn't have a problem capping 60fps.