Created a fresh world in Minecraft version 1.7.10. After first loading chunks I would get between 50-80 FPS.

Created new world with same seed in the 14w29b snapshot. After chunks load I was getting between 20-25 FPS. Occasional freezing where everything becomes unresponsive for up to 20 seconds. Low frame rate was unchanged when VBOs was turned on or off.

All other video settings the same in both test worlds.