I am currently watching Wimblydon on such a setup. The latest MythTV is excellent - it now supports watching/recording different channels on the same multiplex, which is very useful.
Anyhoo - MV is right, it's quite a task getting it all running; though it has to be said, the current version available via apt in Hardy Heron all "just worked" out of the box. How much that is due to me knowing what I was doing having set up several other installations before - well, probably quite a lot really.
As a primary home system - forget it; use a Humax.
For rather more specialised uses, MythTV has a place. Eg: My Mum can't get C5 and is a Neighbours fan. She is also blind, so uses the Descriptive dialog which is broadcast with Neighbours. I've scripted auto recordings and DVD burning with MythTV - and this is where Linux shows Windows up for the stone-age tool it is; all I need do is put in a DVD on Friday morning, and after Friday's episode it does various Advert removal tasks, then burns a DVD with a nice menu, containing 5 episodes of Neighbours, ads removed, with Descriptive Audio channel mixed with the main audio.
It took me fooking ages to get it to work. I have better things to do with my time really!