I have not personally used it, but the documentation at http://www.chromium.org/nativeclient/pnacl/building-and-test... indicates that it is at least capable of running spec2k. I don't know what's complete and what is incomplete. I do know that it is the stated goal of the NaCl project to achieve portability through PNaCl; that alone makes it deserving of mention in this context (https://developers.google.com/native-client/overview#distrib...).