I use an Apple Wireless Keyboard right now with my Retina MacBook Pro. My muscle memory likes the consistency between the keyboard on the laptop and the external keyboard at the desk. The layout and spacing isn’t identical but it’s close, closer than any other third-party keyboard for sure.
This ‘updated’ keyboard isn’t earth-shatteringly different but it seems to be powered by internal batteries, rather than swappable AA’s. I assume the new one will charge by USB or something. From the FCC drawings, it looks like Apple has removed the circular barrel completely. As such, the keyboard will now sit flat which is disappointing — I like how the current one is naturally inclined because of the battery compartment.