New features and enhancements in Spring Boot 2.0 include:

Java 8 is required as a minimum version for running Spring Boot. APIs have been updated to use Java 8 features such as default methods on interfaces.
Java 9 is supported.
Reactive programming support is added via Spring WebFlux/WebFlux.fn.
HTTP/2 capabilities are added for the Tomcat and Jetty servers.
Simplified autoconfiguration is added for security.
Support is added for the Quartz job scheduling library.
Metrics are available based on Micrometer, which provides a façade over instrumentation clients for monitoring systems. Developers can instrument JVM application code without vendor lockin.
Support is added for an embedded Netty server.
Support is adedd for Kotlin 1.2, with the runapplication function providing a way to run a Spring Boot application via idiomatic Kotlin.