HP Entertainment Center Z555 (Pentium 4 3GHz, 512MB RAM, 250GB HDD)

Pros: Lots of audio/video options

Cons: Airflow is critical

Summary: This is a beautiful system. I bought the MCE PC 2 years ago, and because it was a PC, it stayed in my home office. Now that this is the same size as a VCR, its in the family room. I took the Tivo out, and the DVD recorder out, and hid the cable tuners in the back as this provides cables/IR transmitters to change the channels. So my video center looks real, clean! An AMP, the MediaCenter, and the TV.
Beautiful! I'd recommend the personal media drive so that you can copy lots of personal content to the machine.
It comes with an external WLAN antenna so that you're not buying a linksys WUSB12, but you will need to buy an s-Video to Composite video converter if you want two identical comcast cable boxes to connect.
The user manuals are really detailed, well written, and are explicit in their cable diagrams. Hats off to the technical writers; these are good manuals, and I was reading them online before the box arrived (in less than a week!)
You shouldn't compare this MC to a Tivo. I have Tivos and for $400 with service, they're great. But a MC is so much more. Its a PC in the living room, internet radio, pictures, videos, recorded and live tv, dual tuners. what isn't in here? and i read in this review that the graphics card is great for games! bonus!

For your nontechnical elders, who use the mouse as a footpedal, get the Tivo. But for the techy gadget fan, like me, this is the dream system, but it takes a technical aptitude to navigate the Windows PC, which you don't have to bother with when using a Tivo or Comcast DVR.

Included cables aren't enough, you get an HDMI cable, but not a lot of others, so you'll likely be down at the store getting some extra cables, composite or component.

The remote is fine; the keyboard beats entering text from the Tivo remote; and heck; you have a PC in the living room. But beware that text doesn't look great on any CRT tube, so I'll likely be buying a plasma shortly.

heat:
This is like a dense 2u server; heavy and hot! Plan on cutting the back off your cabinetry to allow the heat that this little powerhouse generates to escape.
Its quiet, and if it does get hot, the fan speeds up like a server, and if that's not enough, it shuts down to protect itself. Since I cut the back off my cabinet, its consistently quiet.
Summary: Gadget fan, PC in the living room, high tech, get this PC.
Non technical, get a Tivo or Comcast DVR.
Enjoy