Destroying blocks in survival mode cause them to not drop, anything above them that would normally break off don't, and stay floating. Water or lava will not flow into the empty gaps and mobs remain motionless.
Other problems include issues with creating new worlds without using seed, and worlds that are created with a seed are terribly bugged.
Older worlds work fine, worlds made in this version barely work.
This is very unusual on my computer, which is why I classify this as some kind of bug.