The new release includes a fix for a timeout bug where a legitimate leader could be kicked out of a round before it could submit a proposal. Nodes were elected as leaders and might not have time to submit a proposal, costing the network an extra round. Since the set of validators has changed (there are now more of them), our own nodes cannot maintain a valid branch, causing epoch delays while nodes negotiate among themselves.
Among other things, a small runtime bug for flow execution has been fixed.
The migration announced in the previous release is still activated at epoch 1330000. This hasn't happened yet, so you have time to build a node with the new rules and fixes if you haven't done so yet for some reason.
Updating is very simple - stop the node, run git pull, run sh controls/check.sh, re-run the original controls/config_val.sh, then sh controls/run.sh.
The rest is history.