It means that at the very least the Nvidia specific performance loss of 10-20% will disappear. That is already not an issue with AMD cards as I understand it.
If it'll further increase performance beyond that remains to be seen. I suspect there will always be some amount of overhead, although at least with earlier versions of DirectX it is quite minimal already.
If it'll further increase performance beyond that remains to be seen. I suspect there will always be some amount of overhead, although at least with earlier versions of DirectX it is quite minimal already.