Okay, I've now taken about an hour to test the compositor.
* referencing shaders for aircraft-side effects doesn't seem to work gracefully - the Shuttle is full of broken effects on the grounds that the compositor expects secondary_lights.frag under Compositor/Shaders/secondary_lights.frag whereas it is under Compositor/Shaders/ALS/secondary_lights.frag, i.e. the lookup doesn't seem to take into account that the ALS pipeline is on here
* performance seems to be good, in Hawaii I've not seen any difference to standard ALS - yay!
* exterior shadows look pretty good - the Shuttle launch gantry surely looks nice when the shadow map is detailed enough
* interior shadows are (like with Rembrandt) too flickery for my taste - unfortunately flickering is something I do not tolerate well, it (literally) gives me headaches
* that's pretty bad because low vegetation (and vegetation shadows) show pretty bad z-fighting, making a view of shrubland a rather painful experience for me
There's also substantial z-fighting with scenery models - the shuttle launch ramp in Florida is a rather obvious example
* some planes seem to be messed up without showing a shader error message - the EC-135 basically has grey panels while I didn't see an error message (maybe I just missed it, FG has become terribly talkative...)
* the geometry shader overlay is broken for me, whereas geometry shader grass works fine - not sure why that is as they're pretty much the same bit of technolgy
* some nit-picking, but the shadow map should be disabled when the sun is below the horizon. ALS still uses /some/ amount of light under these conditions - the sky is still bright and offers sort of directional light - however this ain't the light that casts sharp shadows any more as it comes not from a small spot but from a sky hemisphere
So it seems there's still a lot of work ahead - we
must be able to handle aircraft-side shaders and effects gracefully, we simply can't assume they will be fixed one by one, and right now the flickering really is a big problem (I had to end my flight prematurely, got too dizzy...)