With this release, a complete implementation of JSR 3, version 1.2.1 and of JSR 160, version 1.0, is available.
Along with the JMX implementations comes a lot of new features and JMX-related tools.
Most notable are:
Check it out at the MX4J website
View information on the JMX JSRs:
JSR 3: Java Management Extensions (JMX) Specification
JSR 160: Java Management Extensions (JMX) Remote API 1.0