We found some issues with 1.3 (aggregators interacting with nulls/errors, primarily) that we didn't want to let sit until 1.4. So we fixed those issues and a couple others, and added a few 'minor' features. This patch version should be a definitive improvement over the base 1.3 version.
The complete list of changes is in the CHANGELOG. Here are the new options and features:
extendjoin type keeps the type of the first sheet, extending it with columns from the other sheets
rename-sheetcommand (thanks to @jsvine for suggestion; what default keybinding should it have?)
gz^R) to undo modifications on all selected rows