The most valuable feature is its reliability and stability. The first version of BizTalk was released in 2000, and many companies still use it. It was stable until 2013 when we had support.
BizTalk Server offers dynamic scaling with message forwarding for efficient load management and integrates with Visual Studio to enhance development. Its XML conversion into flexible transactions and AS2 protocol are standout features. The business rule engine aids process automation. Despite its complexity and outdated status with no further updates from Microsoft, it remains vital, although it requires physical servers, complicating deployments and updates, and lacks native cloud support, necessitating third-party adapters.