Well this does open up the compiler to be optimized for bitcoin-based applications, though I doubt much gain is to be had.
Similar to how some modify their C compilers I'm betting someone will do the same for us.
Though I do not think it is actually 'open' to everyone yet, just that they are planning on releasing it.
I'm more interested in AMD recently open-sourcing their OpenCL stuffs:
http://www.phoronix.com/scan.php?page=news_item&px=MTAyNjkOf course I am in no way a coder so have no clue whatsoever if that is even relevant.