My computer is not a beast but since the 14w30a snapshot the game is unplayable for me and other people I met on reddit. In 1.7.10 my average FPS was ~50 (WITHOUT Optifine) but in the new snapshots as soon as I move my character a single block, or if I look around, my FPS plummets down from 60 (yes I activated the limiter to 60 FPS and without the limiter it can even reach 150FPS) to less than 25 fps. It's frustrating considering all these new awesome features that have been added to the game. ADDITIONAL NOTES: #the new snapshots are actually playable for me while I'm in a cave because I get no lag (Fps is in the 50-60 range).
my video settings in 1.7.10 are: Graphics: fancy ; clouds:off ; render distance: 8 ; particles: all ; mipmap is at level 4 ; Adv. OpenGL: on ;
In the post-14w30a snapshots everything is on the fastest setting and render distance is set to 6 but still I can only make around 15 to 25 FPS.
I was waiting to see if things get better...and they did in the pre-release...but only by a fraction (Sometimes it goes 60+ FPS smooth and sometimes I get stuck at less than 20FPS
If there is no possible thing you can do to fix this, just allow us to revert to the older rendering method via the video options menu.

[Standing still]http://i.imgur.com/yjGwVs1.png
[Moving around]http://i.imgur.com/NDpXGGE.png