Late reply - sorry.
So which version of MythTV.
0.24 has quite a lot of enhancements around audio playback - but that is only relevant I think if you plan on using Myth-Frontend.
If you're going to use only the backend, and use XBMC for a frontend (and probably mythweb to schedule recordings etc) then you don't need 0.24
However, 0.24 is getting more development and it is the latest...
If you're new to this - go with 0.23 and get up and running quick with MythBox.
If you don't mind spending more time, go with 0.24 and check out this thread on the PVR build of XBMC
http://forum.xbmc.org/showthread.php?tid=110694
The eye of sauron is pointing there...
(Heck, if you just use the myth:// source, you can use mainline ppa and you're up and running against 0.24 anyway.. it's no hassle at all really, just the myth:// source is not as pretty and doesn't have a proper EPG)
The way I see it.. (no disrespect) is that MythBox will 'pause' or fork here and remain the standard for pre 0.24, whereas >= 0.24 will move to the mainline myth:// source or the xMyth PVR add-in as above.
Now - if we could encourage Analogue, tsp42 and dtierney to co-work.. that might be just Amazing