There's also
Gloss, an alternative frontend for mythtv, that's bound to look a lot slicker... and there's the great MythUI rewrite going on for MythTV itself
But then, would MythTV really make sense? Unless you can run it without a server, just using local content (for MythGame etc.), either the startup time would be gigantic (Backend+Frontend) or the backend would have to always sit in the back hogging resources....
But anyway, I think there's a thread about MythTV somewhere already
EDIT:
emil10001 said:
It would also be neat to have finger driven navigation with some of the themes (should work out of the box like that, but you may need to click 'enable mouse').
No, at least not currently. I've been looking into this for an HTPC project and as of now, only part of MythTV (ie the front menu and not much else) has been converted to their new UI library, MythUI, which allows mouse (and thus, touch screen) inputs. The current (well, old but still currently used) one does not.
However, as I mentioned in the beginning of my post, they are working on it, plus the specifications are all there so anyone can make a custom frontend (much like Gloss, which uses the Clutter framework btw... there's a thread about that somewhere around here, too).