I am particularly annoyed with the different brightness on each eye bug, does anyone know of a way of mitigating It? maybe some settings tweaking? Some lighting mod?
The only thing I can think of that's in the power of a user to affect, would be to reduce render FOV down to the point stereo overlap becomes 100% (I seem to recall SteamVR added a setting to draw in the black margins, so to speak), but that is an absolutely terrible sacrifice to make.
As for the billboard sprites for smoke-etc particles, I will agree that their screen-buffer-locked orientation behaviour is not a
bug, (EDIT: ...nor is it uncommon), but it is also not something that
has to be that way -- they could perfectly well be made to swivel appropriately for each use case and axis, to face the camera (not the same as being parallel with the view plane, which is also a problem), whilst maintaining rotation consistency with their emitter.
(EDIT2: ...and the game's "sprite engine" may well have the functionality to do it without needing to itself be updated: You could e.g. have a look at a nearby star -- it has an overlayed lens flare sprite that rotates in this ugly way, but behind it -- if you occlude the centre of the star disc, so that the flare stops rendering, you will see another one much like it, but with smaller radius, representing the star's corona, and that one does
not behave that way -- it stays put relative to the star when you roll your ship; I don't
know that the two are neccessarily produced by the same code module, but it does not strike me as impossible.)