Put the summary of the bug you're having here

What I expected to happen was...:
I updated the game and expect the game to run as smoothly as before no problems.
What actually happened was...:
I updated the game and the FPS rate dropped from around 50 FPS(View: Far everything else default) to around 10 FPS. I still get 50 fps when I use the old launcher but this one kills it.
Steps to Reproduce:
1. Update Minecraft to 1.6
2. Suddenly FPS Drops.
3.