Not sure if this has already been covered.
In my humble opinion, the ability to create a STABLE zoning environment for audio, video and other media is the future of front end applications such as Xlobby.
One of the reasons I chose to support Xlobby say over Meedio, was due to the fact that Xlobby already has zone control for audio (allbeit not 100% stable), particularly in the synchronization area.
It would be great to see xlobby developed to the state, whereby you have the ability to walk around your house and have the control and flexibility to play media in any given zone, either independently or in synch with other or all other zones in the house, whether through the use of a PDA, touchscreen etc.
I think that the fat client route is prob more important than thin client, because ultimately people will want to be able to have zone control of video media (in addition to audio) and so having a physical PC in each zone is prob going to be a requirement.