When I loaded up a new world in Minecraft Snapshot Version 14w27a I was quite excited about the bunnies being added, however, when i join the world, my FPS would not go any further than 15 fps. Usually, I get around 100-130 fps, but now, it's only 15. It's not only the frame rate that's an issue, though. The bunnies seem to jump very slow, and their AI doesn't work correctly for me. I watched my girlfriend playing on the snapshot for a while on her computer, and the bunnies hopped around quickly, they ran from her, they jumped towards her when she held carrots, but for me, they just basically float around and mostly stay in a static position with little particles flying from their feet.
I really hope you can fix this issue by the time 1.8 is released, and you don't ignore this. If Minecraft runs like this in the new release, I won't be able to play anymore. :c