posde mentioned something like that, but it wasn't clear if he was referring to the dist-upgrade you are supposed to do before installing linuxmce, or the upgrade that you do after. Either way, it seems to be working so far. I'm running /usr/pluto/bin/Diskless_CreateTBZ.sh right now and hopefully I'll be able to add MDs without issue, then myth-setup.
BTW, linuxmce found my PVR-150/HDHomeRun devices (installed after initial setup), but even after going through the media wizard, adding them, doing the schedules direct line-up stuff, MythTV doesn't have any TV Inputs defined. I've seen it mentioned in other threads so I believe once I run myth-setup manually I'll be good to go.