I think the Blades are an awesome idea, but I really don't understand your assessment of Apple's usage goals for the iPad. Apple has run commercials promoting creation oriented tasks for the iPad. There is a tremendous consumption market for iPads, but Apple pretty clearly wants it to be a device used for creation as well.

If there is a difference in strategy here, it that Apple's view of how a user should interact with a tablet interface is more direct. I.e., the sliders and buttons showcased on the example Blade would simply appear as interface elements on the display. The Blade idea follows a slightly different model where the tablet serves as a hybrid input/display. The up-side is that the Blade effectively doubles your input surface area. I think that appeals to a lot of people.

In short, I think Apple and Microsoft are promoting a lot of the same ideas here, but I think the Blade represents a bigger commitment to the creation side of the market.

I would assume that the HID (human interface device) API within the Surface's operating system has good support for the development of peripherals like Blades. Does anyone know if iOS has similar APIs for Bluetooth connected HIDs?

ref: http://en.wikipedia.org/wiki/Human_interface_device