Too busy to browse the forums to have your 1.5 question answered? Pick your favorite link.
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http://forums.bukkit.org/threads/how-do-i-update-my-server-to-1-5.134614/

http://forums.bukkit.org/threads/bukkit-1-5.134563/

http://forums.bukkit.org/threads/help-updating-my-bukkit-server.134555/

http://forums.bukkit.org/threads/why-do-some-servers-already-have-bukkit-for-1-5.134534/

http://forums.bukkit.org/threads/1-5-update.134526/#post-1585333