I have noticed that there is a bug where when using an item (Pickaxe, Sword, Food, anything) it duplicates it. Now this sounds amazing, except for the fact that when it does, it replaces another item, sometimes very valuable items like diamonds, or tools.
Another bug is that even when you have been in an area for a long time, mining, fighting, etc. When going into another area, blocks go transparent, and there is sort of an 'x-ray' glitch. While this does not really interfere with game play, it can be annoying.
One more bug that I have noticed, is that even when 5 bars of wifi is being used, the world kind of freezes. I can walk around my world, but I cannot interact with any blocks. The animals do not move on their own unless you move them, and when breaking blocks, they do not drop their respective tile. In order to fix this, you have to exit the world, and wait a bit before re-entering.
Another bug that I have encountered, is that when mining ores that give you XP, like coal, nether quartz, etc. The XP does not go into your bar, but it just floats around you forever. This causes extreme distraction, and interferes with gameplay.