Hi, Jed!
The latest OpenDRT v0.2.4 looks very smooth! And I like how the sliders are intuitive and precise at the same time in terms of the sliders' values that are displayed in UI.
I've noticed OpenDRT doesn't have surround compensation. Maybe it could be added as a gamma slider, that affects tonemapped luminance only, but not colors? Not sure if this is a good idea in terms of perceived saturation, but at least it shouldn't add hue skews that per-channel gamma adjustment adds.
Also I always find it easer to grade under sort of my custom DRT that has your Gamut Compress applied right after display gamut encoding. It allows me to unstick saturated colors from 0. This will make every colorist happier, to see on waveform analyzer how the saturated colors are not crushed, but nicely compressed.
I use one of the older versions, that has shadow roll-off slider, because the latest one that is shipped with Resolve bypasses some dark pixels (I believe this is made for invertibility).
If you don't mind me sharing my thoughts, that's how I see it:
Limit sliders are pre-set based on the selected display primaries.
Threshold slider (or all 3 sliders) is exposed to UI.
Don't preserve the darkest shadows (pre-set shadow roll-off maybe?). I hope for DRT invertibility this won't be a problem (but not completely sure).
And if the (luminance only) surround compensation can possibly somehow create negative values, then, I think, surround compensation should be made over tone-mapped, but linear image, and before gamut encoding. This way gamut compress could deal with the negative values that could possibly be produced by luminance only surround compensation. This would also affect the default values for Limit sliders I guess.
UPDATE.
Ok, now I feel stupid :)
Based on what I've read, from v. 0.2.3 OpenDRT has gamut compression after display gamut encoding. Maybe I just need to play with the values to get what I want.