It is very obvious to me that these keyboards on Amazon are a lot thicker than the MS keyboard (and probably a lot heavier). Look carefully at the thickness of the edge: the MS one is so thin that they had to create a bulge around its micro USB port! Also the Amazon keyboards are using hinges, but the MS keyboard fold is made of flexible material so it is probably more durable.

are you suuuuuuuuuure it's thinner?

http://cdn.pocket-lint.com/r/s/727x/assets/images/phpkhkakk....

Yeah, it's thinner. The dimensions are on the Microsoft Store site: 0.45 inches vs 1.2 inches.

Still doesn't qualify as "reinventing the keyboard" IMHO.

Or this one at $30.

http://www.amazon.com/Perixx-PERIBOARD-805L-Bluetooth-Foldin...

I have that one, and it's very nice, the keys feel similar to a regular keyboard. It also feels pretty solid mechanically when you fold it out. However its not that small. The feature on the MS one to allow easy pairing to more than one device is nice. The textblade looked interesting because its very small. However I would be very skeptical without some third party reviews of people who actually used the device.