Framerate drop between 1.4.7 and 1.5 (Not neccesarily a bug but a major problem/annoyance to players, and I am sure this was not intended to happen).

What I expected to happen was...:
Framerate would not have changed.

What actually happened was...:
Due to the new changes, the framerate has dropped. (I am sure you are aware and many others are but this should not be a problem)

Steps to Reproduce:
1. Play mineraft 1.4.7, play minecraft 1.5
2. Pay attention to difference in FPS
3. Profit

(Attachment not mine so I will simply provide a link)

http://www.youtube.com/watch?v=58SQclDscno