Sun's posted the first official beta release of Java 6 Mustang. I've been following along with the weekly builds, and so far they seem solid. Among other new features, this release includes a new Smart Card I/O API. That sounds useful, but I question why it's in the core instead of being a standard extension. It is a javax package. Does that qualify as an extension implementers are allowed to drop, even if it's bundled with Java 6? I'm not sure.