When I first got an HP Touchpad, the touchstone stand, and the keyboard I understood what the "post-PC" era really was. It was perfect: physical keyboard for productivity, yet a touchscreen with a tablet interface, and the mouse had finally seen its end. The Asus transformer was the next big step, I think. Again, keyboard and touchscreen, but this time a 19 hour battery. If it allowed dual booting it would be perfect…
I'm a fan of the Asus transformer too. One benefit from the keyboard having a battery that I didn't notice till I had been using it this way for a while is that I never charge the tablet directly. When it is low, I attach the keyboard and let that charge the tablet. Then when the keyboard is low I pull that off and charge it. So the tablet itself is never tied to a wall. Psychologically, the tablet feels a hair's breadth away from being a device I don't have to charge at all. The battery state is never in the way of me using it.