In my experience, the best features JBoss offers include the modular architecture where the services are loaded when needed, and the cross-platform compatibility that allows it to run on any operating system that supports Java. The high availability and clustering, distributed support, session replication, and load balancing using Infinispan stand out. The security enhancement such as native support of OpenID Connect or JAS for flexible authentication is another outstanding feature. Others include flexible deployment modes and control of session affinity, which is fine-tune control over load balancer stickiness strategies for managing web sessions. Furthermore, global directory support allows for easily adding shared modules to deployments without class path. It stands out because it is a full-stack platform for building today's cloud-ready Java applications that are scalable and secure, blending enterprise-grade features with open-source flexibility. It is the top choice for organizations that need reliability today. For underrated features, server group in domain mode allows grouping servers and applying configuration or deployments across them simultaneously. Not many people know about the CLI scripting with batch mode or Vault and Credential stores, where sensitive configuration values can be stored without hardcoding them into XML files. Additionally, built-in metrics and subsystem isolation, where every subsystem logging, messaging, or web services can be tuned independently, provide fine-grained control over performance and behavior. This is why subsystem isolation is important, and many administrators have not utilized it that way.