I've tried meedio and was not impressed. It's too complicated to set up.

I've also tried snapstream beyond TV, Intervideo Home Theater Platinum, SageTV, MyHTPC, and a host of others. No commercial solution offered the configurability I wanted from a HTPC solution.

The best solution that I have found, is a open-source program called MediaPortal. http://mediaportal.sourceforge.net/
It has support for autoloading DVD backups, TV w/timeshift, terrestrial and internet radio, MCE remote controls, IMDB lookup, TV tome lookup, XMLTV (for EPG), Mealmaster recipes, launching outside programs (like your x10 software), USBIRT for operating outside equipment, Weather, and more.. It also has a web interface plugin.. I might also suggest using splitcam (freeware) , VLC media player, along with a few macros and a IM program to cut and paste commands to the program in order to view TV over the web or a local network.

Second best was Sesam Media Center, which is quite easy to set up, and includes a proper web browser configured for TV viewing, internet radio support, but isn't as cusomizable.

Third best was meedio.

As far as a case, a hollowed out old VCR case works best and has a spot for a IR reciever.

Get as large and fast hard drive as you can! Also, use a wireless network card!

The cpu doesn't have to be fast, a 1ghz or better will work fine.

As far as tuner cards,
I recommend starting with a BT878 based cheapo card (less than $20, then adding a fusion3 HDTV card, or a MDP-130 HDTV card.

For remote controls:
Girder can't be beat. In fact, you can program girder to load new GML files on a remote button press to give more than one setting per button on your remote. Personally, I use a kworld remote that came with one of my tuner cards and a packard bell fastmedia remote (available for $5 at http://www.isellsurplus.com/product.asp?id=7601&c=13&s=68 ).
I also use a Gyration optical suite with 50ft range, a 2.4ghz video sender, a wireless dance mat (for Dance With intencity/ Pydance), a Saitek P3000 wireless controller for games.

Other suggestions, some tried.. some not.
Use the CDG plugin with winamp to add Karaoke.

Use Nitrous VoiceFlux (Freeware) for voice control! (warning, sometimes TV commercials can activate voice commands, maybe I can use a girder button configuration to mute TV for voice commands, but it kinda defeats the purpose..) Maybe I can incorporate remote microphone for voice command on mine later. :)

Use a voice capable modem for caller ID, call answering, and call recording (with the right software).
Use a Homeland Security Camera ($20 walmart) to add survailance capability.

There's more I can add.. And more that I've done.. But, this post is already getting long. So, I'll let somebody else continue..