Ageia, a company which specializes in physics middleware software and hardware is holding back the commercial launch of its PhysX physics acceleration card. Apparently the manufacturer, ASUS, feels that the market isn't ready for the card yet. With all the Xbox 360 buzz around at the moment, it's not suprising they feel this way. The fact that they've apparently had very little support from game developers probably didn't help either.
Mac gamers will be disappointed at this news. Havok (a rival of Ageia) has long held back the possibility of certain ports to the platform. Ageia's PhysX is being developed with the support of a key Mac porter and publisher, so it's therefore in the interest of Apple (and Mac users) that Ageia does well.
