The nightly build is compiled from the current development snapshot found in the repository. Because of that, it might not have been tested much and contain serious bugs.

     9646735 Oct  9 19:43 Jomic-Installer-nightly.jar
    10851952 Oct  9 19:40 Jomic-nightly.dmg

The last build completed successfully at 2011-10-09 21:44, more details can be found in the build log file.