This video demonstrates just how good parallax occlusion would actually look when using a 256x texturepack. The GLSL mod can incorporate shader effects into minecraft providing you have a strong enough video card!
Although the depth of field can work on almost any texture pack, parallax occlusion (bump mapping) and specular mapping will only work on certain texture packs of a certain size. Parallax occlusion mapping gives the illusion of 3D on a 2D/Flat surface. Here is a demo in CryEngine:
The texture pack for the Minecraft video is called the LB Photo Realism texture pack which are 256×256 in size. Most other texture packs and minecraft itself are run at 16×16.
Here is another example with various different textures on display for demonstration: