karavite,
sorry, even if I work now in electronics, I studied physics... and my title is more research oriented than engineering. that's just for the small story. and today I do marketing... and what I'll try to explain here is more Product Marketing than engineering.
What is the problem with Mac (iTunes) and other cube-like PCs ? The customer considers it's a computer. Of course you can listen to your music (I'm listening to The Turtles right now), watch your DVDs, or even watch/record TV with a minimal extra hardware. I can remote control iTunes and iDVD with my T68i cell phone. The screen of my 17" iMac is not much smaller than the 22" screen of my B&O TV set. But if the TV set, the CD player, the FM radio are though from the beginning to be used just for entertainment purpose, the iMac is not: it has a keyboard, a mouse... when I connect a peripheral, I do that over USB/firewire (1 to several) or Ethernet (which required some complex addressing before Rendez-Vous). So the iMac can be used as a digital entertainment center... but it is NOT an entertainment center.
Now, imaging the same iMac without a wired keyboard and mouse, but with a remote control, starting by default in a mode where TV is the input, switching to DVD or CD when you insert one, one key press launches iTunes... the Bluetooth keyboard being optional. No multi-user (at least not visible). Imagine that when you want to connect another peripheral, you just plug it and it recognizes it automatically (Rendez-Vous). It still connects to Internet via Ethernet for access to CD databases, to iTMS, to Pay-per-View TV... this is Home Automation (in the American Style... in Europe "Home Automation" is more security/comfort oriented, what you name Building Automation, like HVAC control, video surveillance). A Bluetooth enabled 20" iMac is a good start if the system starts directly in full page iTunes with possibility to go to DVD player or iTV/QuickTime or iChat, always full screen like you do with your stereo (you don't play the movie on your home theater at the same time you listen to a CD).
So they have the hardware (for long time), they have the software low level routine... they still must enable the top level application layer so that we feel we use a stereo, or a TV, not a computer (even if it's a Mac).