Since switching from 1.7.9 to 14w19a, I have been seeing a significantly lower fps at all times. In 1.7.9. I run 100-140 FPS and around 20-50 FPS in 14w10c, 14w17a, 14w19a, 14w20a, and 14w20b. I have tried lowering all settings to minimum, and still get the same low fps.

i5 760 @ 2.8 GHz
8 GB Ram
GTX 660
Fullscreen

I have 2 1920x1080 displays

A friend also reporting same problem.

i5 3570K 3.4 GHz
32 GB Ram
GTX 780
Fullscreen

Also has 2 1920x1080 displays