i've tried the xbmc-pvr (with yavdr / yavdr.org )
its not quite 'there' yet... it does work but the 'waf' is very low here. (wife acceptance factor)
too many crashes still (at least for me) and EPG not quite working well.
that said, i do have xbmc installed on my htpc, works quite well.
i would still like to use xine as interface :/
i use xbmc for other things, i would love to use it for live tv as well... but honestly, it is not quite ready yet. imho.
mythtv.... i dont mean to insult anyone here using this... but my opinion is very low of this solution. just a terrible interface, setup, configuration. at least when you're dealing with satellite tv.
i know some folks out there got it to work quite well. to me it is absolutely bloated and broken.
.. myth vs xbmc there is no question ... xbmc is a winner on every single possible comparison.