I think this would be a great idea, but I think it will be or should be the iMac. I would love a true desktop computer set up but have the ability to take it anyplace in my house to surf, watch a dvd on my computer, edit movies watching them on my tv instead of monitor, and actually now that I think about it it would be cool to have the monitor span to the tv where you could take this monitor off the stand at your desktop, into your tv room and edit movies using the tablet screen to edit and use your tv as an extra monitor. There are so many possibilities around the house for a portable screen/computer. You would not need the keyboard cause it would be a tablet, although you could use the keyboard I guess, but would be awkward.
anyway, lots of ideas here, but many I would personally love to use. I know I could get a similar set up on a laptop, but the iBooks only mirror screens, don't do all the things i am talking about doing wirelessly as easily, etc. without much added cost, etc.