Server 1.6.4 its ready. Now we have to wait good plugin source for "magical tricks". And Rainbow will be up as it is and better with the newest version and new plugins.So... do not update your client yet.
Minecraft release 1.6 has come and SOON our servers will run on this version also. But for now we are still 1.5! If you have accidentally updated to 1.6 you can downgrade it. How to? right hold the window button and press R, type in %appdata%, go to .minecraft, right click "bin" and select properties, go to older versions, then click an older version of .minecraft and then click and apply.