Umachandar Jayachandran (or, as we all know him, UC) makes an announcement:
We are excited to announce the private preview of native JSON type and JSON_OBJECTAGG & JSON_ARRAYAGG aggregates in Azure SQL Database. The JSON type will allow you to store JSON documents in a native binary format that is optimized for storage and query performance. The ANSI SQL compatible JSON aggregates – JSON_OBJECTAGG & JSON_ARRAYAG will allow you to aggregate relational data and transform the data into JSON documents in a query.
I do have to admit that the native JSON type was a bit curious, given that they had assiduously rejected the notion of introducing a native JSON type for years, yet here we are. But if there are significant enough performance gains—and there can be by moving from text to binary JSON—it can be worth it. The XML type also allowed you to create indexes, which is probably easier to do with a native type.