One of roadblocks in my opinion to actually doing sketch level design in cad in general has been the indirect nature of drawing with a mouse as opposed to a pen directly on the media. It seems to me that the natural evolution of displays will be back to "digital paper" on which one could draw directly. The current available technology that allows this is the tablet PC, as Revit gets refined as a design tool, I would love to see Revit take advantage of this type of technology. I can imagine taking a tablet PC out to a site and sitting down in the middle of the lot and actually sketching out a design. Has anyone used Revit on a tablet PC...?