I'm happy! No. more. damn. lag. spikes! in my nether anymore.
I've allocated 2GB of ram to Minecraft, instead of the standard 512MB.
(If you're wondering why that number is so low, I'm running 1.5.2 with a bunch of mods, not 1.100 or whatever. It has 5 big bugs I can think of, and the nether lag spikes was the biggest one. Now it has 4 big bugs, but they're not too bad.)