The official release notes for Update 3: Lost Legends of Eriador have been posted for your viewing pleasure. There are also a set of separate store release notes available.
For your convenience I’ve combined both sets of release notes into this single handy dandy PDF!
Scheduled Downtime for Update 3
The LOTRO Game Servers will be brought down on Monday, May 23 from 6:00AM – 11:00AM Eastern (-4 GMT) to launch Update 3: Lost Legends of Eriador.
Source: LOTRO Forums