Chests are broken. Confirmed. You can put items on them and retrieve items from them, but sometimes the items are ghost-transfered and the UI shows them on the place they're supposed to be until you try to change that slot and you see the changes revert to before you touched the chest. This can mean that spare sword or pickaxe or ton of materials for construction you picked for going to the depths of the mine can suddenly teleport back, or rather, tell you they never actually left the chest, while you are neck-deep in a risky situation.
This gets even more insane when your inventory decides you never actually swapped those tools, one almost depleted and the other new, so you end breaking the tool for a mistake caused by the UI not syncing with the real inventory status.
I hope Dinnerbone reads this, because it's the most annoying.
Dunno where to report bugs but I will put it here and someone can carry it over, this one is really weird, when water flows into an area where there is a dirt block 1 block above the ground with anything under it or nothing as far as i know it gives you suffocating damage that seems to be sped up or slowed down. I was in large biomes world in a jungle biome.
The block under the dirt I first discovered was with stone. so a dirt over stone with water flowing 1 away from the source block.
Cave spiders are really screwed up. I had two spiders repeatedly climb walls on the stair case inside of abandoned mineshafts and refuse to acknowledge me. I could not hit them until I literally stood inside of them and swung my sword.
Unfortunately I picked up the water, but when it was flowing into a corner with gravel on the wall, I kept getting damaged if I stood there.
Scoring is not working. Tried the Flatcore Challenge and tested it before I wasted my time, here is the result:
Also, I kept falling through the world when entering the nether sometimes, not sure if that is specific to 1.3 or not, but it's bugged, there's a fireball stuck in the sky and my nether portal duplicated itself, perpendicular to the original. Again, not sure if that's a bug but figured I'd put it here just in case.
I don't know are these two a bug or not but grass grows under water also. and if you sprint on leafs, cobblestone particles will come from your feet. I noticed these while i was using a texturepack but i tried also with the original one and it still did that. Don't know why is it doing this but its not that big of a deal.