The Command to enter login items is not working in 10.8
I didn't have AutoLaunchedApplicationDictionary in ~/Library/Preferences/loginwindow.plist but only in /Library/Preferences/loginwindow.plist.

Most login items are stored in ~/Library/Preferences/com.apple.loginitems.plist. The paths are stored as alias data, but you can also add login items with AppleScript:

osascript -e 'tell application "System Events" to make new login item at end with properties {path:"/Applications/TextEdit.app", name:"TextEdit", hidden:true}'