Lots of updates, fixes, and changes, so it's probably easiest to visit our changelog to see what's new.
As always, you can update your SDK on macOS by clicking "Check for SDK Updates…" under the Simulator's app pull-down menu. On Windows and Linux, please visit http://play.date/dev and download the new installer. (From here on out, Windows and Linux users should get automatic updates of new SDKs via the Playdate Simulator app!)