Releasing a demo is good for everyone, period. Making a demo is comparatively easy for Valve, as they don't add extra maps, etc. - they take the existing maps and perhaps modify them somewhat, but generally, there's no large-scale creation effort. It's good for people who want to see how HL2 performs on their computers before they buy it - now anyone has the chance to test his hardware. It's good for ATI because it brings them more publicity (yes I don't like them, but it's good for them regardless). So if someone is upset that Valve released a demo instead of some other content, stop being egoistic. Valve is right to want to attract new customers and not only please the existing ones, besides, the game has only been out for a month, and in that time we already got HL2DM and a new map for CSS, all for free.