I use SageTV with a the HDHomerun and record HD local channels for free off Comcast. They also have some of the nicest extenders. SageTV can play pretty much anything you throw at it like ripped DVD's. I had a copy of Beyond... not even close to being at the same level IMHO.
There are many here that use SageTV.
A second choice would to just use Win7 Mediacenter as I hear good things about it. Not sure about the extender or HDHomerun support. There is going to be cablecard support soon for Win7. When that happens I might look at changing my setup but for now my wife loves getting to record up to four HD shows at the same time (I added a second HDHomerun when the networks decided to cram a lot of good shows on Monday nights).