Over at Tech Report they have an article up describing the latest Half-Life 2 debacle. It seems NVidia's newest graphics cards don't cut the mustard when it comes to Half-Life 2. Specifically 30fps on a Geforce 5900Ultra when a Radeon 9800Pro gets 60fps. All the Geforce cards go downhill from there.
The article details a presentation made by Gabe Newell at ATI's Shader Days event which depicted the disappointing performance of NVidia's chipsets and even took shots at thier benchmark "tweaking". They stated how NVidia's latest drivers would try to remove visual quality from Half-Life 2 to gain performance, while the game was in development. To quote one of the slides Mr. Newell presented about the various ways drivers lie to benchmarks "Our customers have traditionally made purchase decisions based heavily on benchmark data ... (because benchmarks are lied to) our customers will be pissed."
The presentation also detailed how Valve wrote an NVidia specific path that was apart from thier DX9 graphics renderer path, the results were still disappointing. Valve also stated they were as surprised as anyone that NVidia's hardware didn't handle Half-Life 2 very well. Long story short, if you want to play HL2 with your newest NVidia card, you're going to have to lose some of the eye candy.