A chatlog on qith Valve Software at ModDataBase.com reveals word by Valve's Gary McTaggart: "Anti-aliasing has been fixed for all cards." This is actually good news after the recent discussion if and under which circumstances HL2 would be able to run with Anti Aliasing enabled. Further of note is that Valve will be delivering a detailed benchmark before the game ships, where you can run a particular card through any of the DirectX levels where appropriate..