When in creative mode i flew up on a whim after placing some carpet down, after i got 50-ish blocks above the carpet i looked down and noticed that they were partially invisible, how invisible changed with how i high i flew and the angle of the camera.
(found from build 5 up.)
How to Reproduce:
1. Place down some carpet. Any color should do the trick.
2. Fly up and look down at the carpet until it turns invisible. You should notice lines appear on the carpet as you start getting higher.