It works!! I installed XBMC on one of my computers, enabled all the uPnP features, and the Thunderbolt is now streaming media directly to that computer AND controlling the playback in real-time (pause, play, change media, etc.). My phone is the remote control! Keep in mind that NOTHING needed to be installed or configured on the Thunderbolt. Just go to the Gallery or "Connected Media", select an item, then Select Player, choose the XBMC, and the video starts playing on the remote device.
Apparently, none of the 5 other devices on my network support this Thunderbolt feature (Logitech Revue w/Google TV, XBox 360, and 3 PCs running Windows Media Player 11 with media sharing turned ON). All of these devices can share their media with each other, but the Thunderbolt cannot play media directly to any of them or control their playback. I wonder why.... ideas, anyone?