In the new snapshot 14w31a with the performance Improvements I get bad frame drops when moving across the world, I usually get 60 - 90 fps in 1080p but sometimes it drops to 6 fps when moving across the world.
As you can see in the first attached image my frames dropped to 19 and I think just before it happened the chunk updates were in the one hundreds, I really need this bug fixed because it is making the game unplayable and if its in the 1.8 release I will be very sad, the second screenshot is what my frames are meant to be at (60 - 90) and the third one is another frame drop.