Yeah, so this is the same as gnome's gconf settings for NetworkManager preferences.<p>But that being said, the plist file format isn't all that great (there was a time when Apple had binary "compiled plist" files, but the pl command no longer supports that) -- the alternating "key" and value tags only associated by order in the file is kind of anti-XML.  On one of my Xserves with two interfaces active, this file is 9k, massive for its purpose.  This is not something that even an experienced administrator would want to edit using anything other than the GUI, doing so would be quite error prone.  So if you want your settings to stick, you should be doing it from the GUI on OSX.  The complexity of doing it from the GUI in a way that sticks and from the command line in a way that doesn't stick are roughly the same, but the results are different: to get it to stick by editing from the command line is quite a bit more complex.