When using snapshot 13w16a, I get extreme framerate drops as compared to 1.5.1. I used to get way over 60 fps on high settings, but in the new snapshot, I hardly get 30 fps on high settings (see pictures included below).

As you can see on the pictures, the differences between fps is (funny enough) 100 fps.

Setting the settings to lower values gives me a slightly higher fps, but not much. Playing on my survival world is almost impossible, unless setting every setting to low (which also won't give me my usual framerate). I know it's a snapshot, but I was not sure if you were aware of this problem.