In a nutshell, I had to move all the small chunk decorations that are normally done after a chunk is created, like ores, small trees, plants, etc, into the actual chunk creation itself. In effect, this sent the entire chunk, pre-decorated, as one big packet, instead of hundreds or thousands of block updates. Network packet overload was the cause. I killed it.
All five dimensions are now faster. Most significantly, the Island and Crystal dimensions are now lag free. Wow. Talk about a big change in playability! I don't normally like to do releases back-to-back like this, but the change to the game itself, the enjoyment thereof, is huge.
Go, fly around the Islands dimension, explore the Crystal dimension, and don't fear the lag monster!
Oh yeah... There's also a little Valentine's Days surprise!