I've done some analysis on the shadow settings.
3 distinct scenes to hopefully capture the behavior in most common situations.
First scene:
medium - 85 FPS:
high - 83 FPS:
very high - 77 FPS:
contact hardening - 74 FPS:
Apparently, CHS isn't on for this light, though I thought this scene would be a prime candidate for variable penumbra. Still has a performance impact though. Also, here "medium" doesn't really look much worse than any of the other settings.
Second scene:
medium - 82 FPS:
high - 81 FPS:
very high - 78 FPS:
contact hardening - 69 FPS:
Here, all the settings have artifacts, terrible ones for the medium setting. CHS works pretty well and looks by far the best out of all the options.
Third scene:
medium - 82 FPS:
high - 81 FPS:
very high - 76 FPS:
contact hardening - 70 FPS:
contact hardening ultra - 64 FPS:
Here we see the primary issue with the CHS implementation -- shadows outside of the first or second cascade (I assume) are completely lost. Where they do work, I'd say they are pretty neat. But in this scene even "high" doesn't look bad, too bad that there are also situations like scene 2.
Overall, I'd appreciate an option that does the same as CHS non-ultra but doesn't refuse to work for more distant shadows. Having CHS apply to all light sources would also be nice.
For now, I'm going without CHS, and based on this analysis it seems like dropping down to "high" shadows isn't a bad idea for anyone who doesn't have GPU power to spare.