File locations:
All support files are being stored in:
~/Library/Application Suport/com.turbine.lotroclient/
lotro.keymap
lotroclient.log
Chat logs (Capture Chat)
Screenshots (F11)
Music (folder) -- ABC Music files
Plugins (folder) -- Lua Plugins
PluginData (folder) -- Lua Plugins Data
ui (folder) -- Skins and Layouts
The "UserPreferences.ini" file (as found in the Windows Client) is stored as a plist file:
~/Library/Preferences/com.turbine.loroclient.plist
And the launcher
~/Library/Preferences/com.turbine.lorolauncher.plist
Note that .plist files are "binary" files which need to be read and converted into readable text. Xcode (free from the App Store for Mountain Lion users) does a fine job as do other third party text exiting programs. TextEdit cannot read or convert them. (TextWrangler - Bare Bones Software can convert them into XML form, however the resulting file contains all of the Apple plist boilerplate which tends to make the resulting file less than readable and therefore useful.)