You know what else this means, right? All their Mac games will be running on the latest version of Source. (You know, like how they planned for Source to work in the first place but changed their minds when it turned out to be too much work.) So things like multicore support and the new VPK file system will probably be available in Half-Life 2 and stuff. And I can't even imagine what they're cooking up for the SDK, seeing how they're having to build most of the tools from scratch and have plenty of opportunities to tweak and improve stuff.