With the change that causes block breaking to reset when you change tools, there is an annoying side effect on laggy servers. If there is a delay between the time when you break a block, and the block actually "pops", when the block actually breaks, if you were in the middle of breaking a second block, the block breaking on the second block resets.

How to reproduce:
1. Login to a server that has a little lag.
2. Break a block.
3. Immediately start breaking a second block.
4. When the first block "pops", your second block breaking will reset.

This is annoying especially when you have a decently fast pick, because you have to "break" every block twice before they actually break.