Okay, time for geek post...
At first I wasn't happy with some features that I had with other rented DVR's but then realized it wasn't that the features weren't there, it was my IR remote was missing some of the necessary buttons. One of those features was the OSD (On Screen Display) while in LiveTV mode but I fixed this by mapping the remote's Home button to the M key. Now I'm happy.I got my MythTV DVR completely built and hooked up. I based it on a JetWay J7F2WE1G2E (Mini-ITX motherboard with a fanless VIA C7 CPU), a Hauppauge WinTV PVR-500 Dual Tuner Card, and the IR Remote and Receiver that my ex-boss gave me from his old HP Media Center computer. I wanted to get it running on CentOS 5 but could not get the hardware based XvMC (X-Video Motion Compensation) drivers to work no matter what I tried so I finally gave up and installed Fedora 10. With both tuners recording and watching in LiveTV mode, CPU usage averages about 45%. Without XvMC, this would have been much higher. When just recording and not watching, it averages 9% CPU. The icing on the cake is that it draws only 21 watts total.
If you attempt a similar setup, i have some suggestions. Remove Alsa emulation in PulseAudio and install the real Alsa modules. This cuts down CPU usage quite a bit. I also tried using TWM as the Window manager but decided on using Xfce instead. It is also important that you install the msttcorefonts package otherwise nothing will render correctly.
If you have any questions, drop me a note.