I have been checking out the Delll XPS 12 Tablet / Ultraportable Laptop and found that when I plug the power cable in the touch pad and touch screen stop functioning properly. I found that by touching the metal outer casing that both the touch pad and screen became more responsive. However I was also able to feel the current, as in a slight electrical tingling, whilst touching it. For a laptop that costs between £1000 to £1400 normally this isn't exactly a good show, and as far as I can see there are quite a few other reports from others saying they have the same problem.
I have already installed the latest drivers, however I think this is more of a hardware issue. If it wasn't for this issue I'd say this is a great computer, but I personally couldn't afford to risk having a PC that might stop responding at the wrong moment.
Also the screen tends to brighten or darken occasionally unrelated to the power settings.