When I open a world, about 50% of the blocks have the "Missing Texture" purple and black texture. The blocks still work correctly, but the textures don't.

Also, I spawned a Guardian on land and it went up in the air and moved along in short, jerky movements. The animation for it is also REALLY fast in comparison to how they looked in SethBling's video of the snapshot.

And, all mobs are moving in short, jerky patterns. If i punch a pig, it goes in the air as normal, but moves to the ground in skipp-i-ly. (So Grammar. Wow.) Plus, the chickens are flpping their wings really fast at all times.

I posted a video explaining the mob stuff here: http://goo.gl/2D3SCm
Sorry for the bad video, my PC is not good with recording, but runs minecraft ok.