Actually, since Apple actually is a big partner with OGL and actually uses it in its desktop, might be better of with AMD and the new HSA foundation.
Apple, like it or not, has very good hardware and software for video and sound, which actually is easy to accelerate with GPU muscle. Besides, Apple has always loved eye candy on their desktop, so going with AMD might help in that regard a lot.
AMD would just have to step up their driver's game, but other than that, sounds like a pretty good deal for both.
Cheers!