• Actually affects 0.9.0 builds from 1 to 4

Greatly slows down mining.
Light is not recalculated when digging or placing non-emitting blocks (Almost everything except torches, lanterns and glowstones). At the place of newly removed blocks the light is always zero. Must place or remove a torch to make light recalculated.

See picture (Both survival and creative):
Pic 0 - Naturally generated ores
Pic 1 - One layer removed (Bugged)
Pic 2 - One more layer removed (Bugged)
Pic 3 - A torch placed inside the hole (Well)
Pic 4 - Torch removed (Well)

Thanks.