Try looking in mythtv for a linux alternative. I know a few people running mythtv and are fairly happy with it. The main problem I have even thinking about using mythtv is support for various capture sources seems difficult to setup.
GBPVR may have problems but recently I've found it to be fairly stable. Stability in my environment is probably the most important requirement. Meaning that it needs to be usable by both my wife and kids.
Both mythtv and gbpvr support (mythtv to various degrees) mediaMVP.
One thing I would like to see in regards to GBPVR is an easier way of find the current/reported problems. Searching through this forum sometimes is a lot of pain to find a problem. Maybe another sub forum would be the solution where sub was the only person that could create threads.