It wouldn't be a big deal if they lock out AMD and give AMD nothing but problems working with it... AMD literally can't crossfire in these games it just breaks their drivers. That's been consistent with every game so far. Witcher 3 is the only game currently that supports AMD very well while supporting Gameworks.
I understand it's a great tool and very beneficial for devs, I don't deny that, but Nvidia are just using it the way they are to force AMD out. They are just using their marketing power over them.. Cons outweigh the pros here.
/rant