Ever since I updated to 1.8, I've had issues with chunks of the world loading slowly. Really slowly. I can fly out into nothingness for several chunks and look back for quite some time before they load.
In fact, it's actually possible for me to fly down into a cave on the edge of a loaded chunk before the one next to it loads. When they finally do load, I get pulled back up to ground level, so I don't get trapped down there.
I've never had this issue before, and (unless 1.8 changed them automatically) I haven't changed any settings.
I saw a similar bug report about 1.8 being slower, but as far as I've noticed, it is ONLY world generation that has slowed down for me. Everything else runs at normal speed.
WAI. MC-63093