" e: thought this was new but guess not?"
New video showing the performance difference between Mantle and DirectX. They also mention there are 3 games currently in development using Oxide's Nitrous engine (Star Control which has been confirmed plus 2 others).
AMD has announced that three more game developers have signed up to use the company's new graphics API, Mantle.
Cloud Imperium Games, Eidos-Montreal and Oxide Games will all start using the technology to help optimise the performance of their games when using AMD hardware.