Minecraft 1.7.4, Minecraft 14w07a, Minecraft 14w30c
Windows 8 x64
I just found, that nether and the_end tend to lag.
And so I began investigating.
Here's what I found:
Smooth Lighting setting does not work in the worlds nether and the_end.
Let's say I have turned Smooth Lighting off, I enter the nether, and regardless of my setting, Smooth Lighting always stays ON.
Nether is safe from this bug.
The_end still seems to be affected by this bug.