you can check this link which contains the statement:
Important note: SwingX 1.0 is the last release targeted at Java 5 (JDK 1.5, "Tiger"). Immediately after the release, the codebase was - in fact, still is - moved to target Java 6 (JDK 1.6, "Mustang").
the recent activity on the forum indicates that there are in fact many current users.
