I have just fixed the shadowing/lighting issue that caused excessive darkening of grass, fences and other things. I can now tweak the exact amount of shadow each block casts, as opposed to all-or-nothing solution that was there before. I had to refactor the lighting code slightly, but I think the new one should not be any slower.
This is how it looks now:
On this screenshot fences have shadow of 4, grass 8. Previously everything had shadowing of 15.