while this is not for every application....
We currently have 24" iMac in the kitchen, mounted to a wall- with an EyeTV device attached. I will say that it is very useful to have a combo TV/Computer for a spot like this... takes up limited space, and serves both needs quite well.
Its not the best place to unwind and watch a film, and we dont really watch that much TV on it- but when we do want TV in the kitchen, it comes in very handy.
I could see where using the iMac as an HDMI monitor would be of use too...
I wonder if you'll still be able to use a "box" to receive premium channels from a provider, or if this "tuner" concept is strictly provided by Apple via iCloud and they will provide the content.... (well- it is Apple.. I think I already know the answer to that one)