Microsoft's StartKey: Computer Environment on a USB Stick. I've Experienced This Before and It's Awesome
StartKey will be a technology that allows you to carry your Windows logon around on a USB keychain. Early reaction is mixed as to the value of this, but I loved something similar when I worked for a company developing software for Sun JavaStation network computers.
With JavaStation's, you had a smartcard that you plugged in and, after 10 seconds or so, up would come your desktop. Since most of the time you work at your desk, most of the time this was not particularly valuable. But let me tell you -- it was fantastic for meetings and presentations. No messing around with cables and display settings, no hand-waving when trying to describe an issue you were talking about when you happened to be on the other side of the office.
The difference is that the JavaStations were uniform hardware, too, and all your software lived on the server (which, it turned out at 7AM the morning of a major trade show, is a single point of failure). While you might have a good experience assuming that a random machine has Office on it (a smile creeps across Microsoft's face), there would presumably have to be a solution for specialist software such as Visual Studio or Photoshop that could not be assumed to be local.
I would think the problem with that is that although memory sticks are probably getting capacious enough, the bus connection between the memory sticks and the main computer are going to be bottlenecks.