A few properties of Operation objects have changed. In an effort to standardize and streamline operations, their properties have changed. This won't affect 90% of use cases, since operations are usually low-level concerns. However, if you are using operational transform or some other low-level parts of Slate, this may affect you. The value, selection, node, and mark properties—which contained references to Immutable.js objects—have all been removed. In their place, we have standardized a properties and newProperties pair. This will greatly reduce the size of operations stored in memory, and makes dealing with them easier when serialized as well.