Frooby, et al,
Don't give up on this project. From the most recent traffic it doesn't appear that elupus is committed to making the new xbmc myth work on xboxs. The functionality is still a long way from this script, so hang in there. Please keep this alive until the same capability is available elsewhere.
FWIW, I'm not having any problems using the myth:// protocol support now officially in XBMC on the XBox (although I'm not using Live TV yet - will be once I get Digital Terrestrial setup on a new Linux HTPC).
Alcoheca at xbmc.org has started on the Google Summer of Code (GSoC) to put in PVR frontend capabilities into XBMC which should encompass many of the things that the xbmcmythtv script provided (talking back to MythTV).
I can understand why this script might not have much more effort spent on it in the hope that the GSoC project will be a success and render the great work that has been done here unfortunately redundant. I can also understand your frustration because that project is likely months away from being usable.
Sadly our XBox is getting replaced - it simply can't play HD content and we now have that available via digital terrestrial here in Auckland, New Zealand.
From what I can see the new mythtv:// work is a looonnngg way from being even minimally useable. Jump forward/back doesn't appear to have been implemented and it hangs frequently.
The only time I still have problems with jumping forward and backward is when a show is still recording. Jump forward and backward works sweet for shows that have finished recording. And with XBMC configured to skip forward over 7 commercials (7 * 30s) I don't even bother with the somewhat unreliable commercial flagging anymore.
I haven't had a hang problem for probably a month now (but I'm not using Live TV).
I'm having problems with the cmyth stuff in the latest (30 June 2008) T3CH build, as described above. Skipping forward/back just doesn't work, and I regularly get a locked-up XBox.
The newish XBMCMythTV plug-in for XBMC seems to work really well, for playing recorded shows only, but is a great start. So perhaps any further work should be directed there.