Awesome...works for me on OS X, though it took a bit of trying. If anybody else runs into the same problems I did (Jar Launcher craps out when trying to open it, even after updating to the latest Java), it might be because, even though you've got Java 2 SE 5.0 (J2SE 5.0), which is what you need, you've also got J2SE 1.4.2 (or some other version) hanging out. Apparently the default behavior is to keep 1.4.2 as the default runtime environment. To fix that, go to /Applications/Utilities/Java/J2SE 5.0 and open up Java Preferences.app, then swap the order of J2SE 5.0 and J2SE 1.4.2 under "Java Application Runtime Settings" in the "General" tab.

Like I said, the above worked for me, anyway, but I don't know how unique my setup is.