I'm on Cablevision and I use an HDHR3-CC. Unless you use Windows Media Center, you will not be able to tune any of the premium channels (HBO, SHO, etc.) or anything marked something other than copy-freely. We've found that those seem to be limited to channels found between 100 and 199. I don't do Windows so I can't help you there.
XBMC's PVR feature isn't there yet and plugin support for the Prime is lacking. Since MythTV has direct drivers for HDHR's the Prime will work with it. Everything else treats it like a DVB device and that doesn't work so well (see below for details).
My current setup (and the user experience is very spit-and-baling-wire) is an XBMC frontend with tsp's Eden-PVR build on top of a MythBuntu distro. While this is "good enough" to watch some recordings if I'm around to manage things, it is not wife-ready (Not mine anyway).
I need a 2nd and probably a 3rd XBMC device. I tried OpenELEC_PVR 1.99.8 (Aug 4) but its MythTV plugin isn't working so I'm debating my next steps. InoD just posted an OpenELEC build with tsp's plugin so I might give that a shot.
http://forum.xbmc.org/showthread.php?tid...pid1181966
Why the HDHR DVB hack doesn't work for the Prime
DVB streams can carry multiple channels. Every DVB client I've looked at performs the final demultiplexing itself so that if it needs to serve multiple channels from the same stream it doesn't have to tie up additional tuners. Unfortunately the Prime doesn't activate the CableCard unless the commands are issued to fully tune the channel (set both the frequency and program number).
Using an ugly hack, I was able to work around that but the client barfed because it detected a crypto stream and there wasn't an option to ignore it. Ripping out the crypto detection solved that in the short term. I suppose I could have written a null-decrypter but cleaning up the hack to make it palatable for upstream inclusion required more effort than I had motivation for.