Bukkit

2.7

• Fixed signs
• Fixed issues with arenas ending prematurely
• Fixed multiple spectating bugs
• Fixed multiple small bugs
• Rewrote the creation process
• Fixed loading errors associated with Multiverse and MyWorlds
• Fixed null or offline players holding up arenas
• Fixed skeletons not spawning with bows in Mob Arenas
• Fixed players not respawning after their first death
• Allow Mob Arena rewards to be configured
• Fixed IllegalArgumentException with healer class
• Added undo command for arena creation
• Fixed conquest arenas
• Added option command
• Save all available player data, then reapply it after the player leaves
• Fixed IndexOutOfBoundsException with CTF
• Check for new and deleted files when reloading
• Fix entity clearing
• Miscellaneous flag fixes

Note: /ua done has been replaced by a more dynamic creation system. Just follow the on-screen prompts!
A complete changelog can be found here

None :)

If you happen to find one, report it using a ticket.