Minecraft wiki entry for Adventure_Update, associated text: There is a memory leak mainly occurring on Linux 32 bit.
The destruction animation for chests is missing.
Lighting persists in water even after the light source is removed.
Experience orbs when dropped don't drop in a stack like items do, so when a player dies when they have a large number of experience, each orb has to be processed individually. This causes a high amount of lag, especially for multiplayer servers.
Double chests placed before beta 1.8 on multiplayer servers all appear to players to be facing the same direction, even when they should be rotated by 90 degrees.
The Item Selection screen in the new Creative game mode is missing spruce and birch leaves, tall grass, double slabs, monster spawner, snow cover, and both huge mushroom blocks.
NPC villages occasionally spawn over partial water areas and 'float'.