Blocks placed or destroyed take 1-3 seconds to render into world view. This occurs with all block types (tested with use VOBs enabled and disabled and Advanced OpenGL enabled and disabled). FPS are usually between 40 and 70, Minecraft has been given a forced 5gb of ram (using -Xms, -Xmx). Tested with latest Java 6 and Java 7 updates for Mac. The issue seems more prominent at longer render distances, but occurs at all distances.

This issue occurs when creating or destroying all block types, but not when altering blocks (pressing buttons, etc) or when attacking mobs. World chunks load fast while flying, with no visible world edge. This issue only appeared upon updating to snapshot 14w29.

To reproduce:
Easiest reproduced by digging a hole straight down in creative mode, then moving across a few blocks, and flying up whilst destroying blocks. The world will not re-render after the block update, allowing you to fly into the previously destroyed blocks, allowing an x-ray view of the world.

This issue can also be reproduced simply by destroying a large number of blocks very quickly in any gamemode (easiest in Creative).