This group is more directed at the people who might build/sell those devices, looking for developers willing to help.
If you want to set up and run MythTV, you should check out the user support options (
http://www.mythtv.org/support), particularly the IRC channel and users mailing list.
Honestly, if you just want a device that can record TV, and aren't interested in tinkering with constantly-changing software, you're probably best off just buying a Tivo. Though it has fewer features, it will give you fewer headaches than MythTV, and cost you about the same in hardware. If you want to set up something on a computer, but aren't interested in learning a lot about Linux, there are also a number of Windows-based DVR applications (including the media center built into Windows itself), though I don't know enough about any of them to provide any advice.
-Chris