After seeing the Harmony's XML format, I think something that viewed and edited it in a regedit-like "tree" format would work well. None of these opening and closing tags, just easy-to-userstand format. For instance:

 CONFIGURATOR
 +-OPTIONS
 | +-OPTION
 | |   -NAME: ScrollShowsByPage
 | |   -VALUE: False
 | +-OPTION
 |     -NAME: ScrollChannelsByPage:
 |     -VALUE: False
 +-IMPLEMENTATIONS
 | +-IMPLEMENTATION
 | |   -TARGET: DEFAULT
 | |   -DEVICENAME: 3575
 | +-IMPLEMENTATION
 |     -TARGET: DEFAULT
 |     -DEVICENAME: 3577
 +-SETUPACTIONS
 | +-SETUP
 | |   -DEVICENAME: 3575
 | |   -OPERATION: SetInput Tuner
 | +-SETUP
 |     -DEVICENAME: 3577
 |     -OPERATION: SetInput TV
 +-TELEVISIONGUIDE
   +-CHANNELLIST
     +-CHANNEL
     |   -CHANNELID: 18380
     |   -NUMBER: 46
     |   -NAME: SpeedVision
     |   -PREFERENCE: Like
     +-CHANNEL
         -CHANNELID: 18141
         -NUMBER: 35
         -NAME: CNBC

Now, with some re-thinking of Harmony's XML tags (so ITEM and VALUE could be displayed on one line, rather than two), things would get even better.