I too have tried mythtv and found it to be a big bloated slow piece of crap. It seems to be a bunch of odds & ends slapped together rather then a solid dvb app built from the ground up. Not impressed with it at all.
I should note that even though I did give it a try, I never intended to replace VDR with it regardless of the test results. I am a VDR loyalist. :)
Cheers, Derek