Mob Arena was pulled due to performance issues on the server (what was causing days/nights to last too long, lava/water flowing weird/slow, etc)
Testing Spout features – purely optional, however there are additional features for those who also use the client.
Download – http://minedev.net/BukkitContrib/Spoutcraft.jar save someplace and launch it – connect like normal.
In game you can see demonstration of what it can do when creating a showcase. Also juke boxes accept a few more items besides records to play custom music (small sample for now)
More to come on this as we test stability and if good, add functionality/features.