Blocks update excessively slowly/irregularly. (Blocks pushed/pulled by pistons render weird, random chunks render/update very slowly, and chunks nearby sometimes un-render)

Example 1: When I open the 3x3 door with the hole in the middle to my potion lab, it takes two seconds (which is normal) to open, but the actual ice blocks appear to still be there for seconds, and sometimes, the lower 3 ice blocks (Y level 47) look like they disappear before the top ones. (this may be related or the same as bug I just reported)

Example 2: Sometimes, when loading a world, some loaded chunks will be invisible for a long period of time, but the hitboxes are visible, and I can walk around on them. If I place/remove a block on them, they're visible.

Example 3: When I load a world, especially creative default-gen worlds, flying around makes rendering chunks go invisible when I go into loaded but un-rendering chunks, causing chunks I enter to appear and the un-rendering chunks to appear but the already rendering chunks to un-render.

Sorry, this may be super confusing..

To clarify, this is the same bug because they are all about chunk updates occuring very slowly. I don't have issues with glitched blocks that respawn when I break them (not since 1.7.4), and I haven't had issues with blocks being visible but not existing (Since 14w34a-ish).