The first step for FSR would be to look better than native 1440p upscaled to 4k, while FSR is operating from 1440p base resolution. I don't think I saw that in the DF video. They said 4K FSR(Quality) has 1440p base res and posted comparison shots for 4K and 1440p resolution in the article though...
1440p Native:
4K FSR(Quality/1440p base):
1440p Native, 720p slice for forum viewing:
4K FSR(Quality, 1440p base, 720 slice for forum viewing):
FSR holds up pretty well from these still shots. Shimmer in motion might be a different deal, and it's hard to ascertain performance between the 2(all the FSR shots were 60fps lock). I agree with DF that it does a decent job at preserving edges, but loses inner surface detail. Either way I'm looking forward to trying it out.