1- The new Turbine Native Mac Client works only under Lion (OSX 10.7.5) and Mountain Lion (OSX 10.8.x). This client can be downloaded directly from Turbine or from Steam. They both are the same client. All patching of the Steam download is handled identically to the Turbine download... i.e. by the Native Mac Client itself.
The configuration and file layout of the Mac Client is quite different from running under CrossOver.
See: LOTRO-wiki.com Mac client for details
2- If you are running a version of OS X prior to Lion (i.e. Snow Leopard (OSX 10.6.x), you should be able to run the recently released CrossOver Version 12.0 (12.0.0.26743). I do not have a Snow Leopard environment any longer so I can not test Crossover V12 on it.
3- If you are running Lion or Mountain Lion you can continue to run CrossOver Version 12.0 (12.0.0.26743) with the Windows client. There is a performance hit, but otherwise, it appears to have only one particularly unique problem. When the game is launched by PyLotRO, the window stays black until the Character selection screen appears, but then works normally.
4- The CrossOver installation of LOTRO continues to depend upon PyLotRO for both patching and launch.
In all cases, (i.e. for both the Windows and Native Mac Clients) Update 8 (Riders of Rohan) has memory leak issues. Update 9 is to be released on 17 December 2012 and may address many of them.