I wonder the same thing. But I would be really interested in trying a small Mac Air sized screen/keyboard shell that had a port that I could slide such a phone in to. Sort of a portable docking station.
Reminds me of my old Motorola Atrix [1]. It had a laptop docking shell that booted a restricted version of Ubuntu alongside an instance of Android. It was totally cool, and everyone that saw it was amazed. However, actual usage was another story. Tegra2 just wasn't powerful enough to drive Ubuntu and Android concurrently in a usable manner.
Our code runs fairly well on the Nexus 4 today, and through much dogfooding, we've learned that RAM is the biggest limiting factor in performance. So when (if?!) Edge ships with 4GB of RAM, the desktop mode will fly.
Why not? Right now, I basically always have my iPhone with me. Often, I also have an 11" Air with me. But there's a lot of redundancy between the two, I have to keep them in sync, and tether the phone to the Air when off WiFi. This sounds like a credible solution to eliminate that redundancy and it wouldn't mean carrying an extra device.
Honestly, I'd probably fund this project right now if they had a tablet or notebook docking accessory in the plan.
[1] - http://en.wikipedia.org/wiki/Motorola_Atrix_4G