X-bit labs has posted an article that explains in detail why Anti-Aliasing may be a problem in Half-Life 2. They got their key information from none other than... HalfLife2.net! The most shocking news of this development is the fact that ATi cards may be able to alleviate this problem, while nVidia cards are pretty much stuck: "The developers of the legendary Half-Life game said that drivers are not likely to solve the problem, however, it still can be solved for graphics cards based on VPUs from ATI Technologies, such as RADEON 9500-, 9600-, 9700- and 9800-series. As for NVIDIA GeForce and GeForce FX-series, there are practically no chances to find a workaround, according to Valve." It's an interesting read, you can find it here.