The reviews are in for AMD's new high-end 3D card--the embargoed, but not exactly secret 2GB Radeon HD 4870 X2--and the official results are as enthusiastic as the previews. By all accounts, the $550 Radeon HD 4870 X2 is the fastest desktop 3D board on the market, outpacing Nvidia's flagship GeForce GTX 280 card on most tests.
According to the results on PC Perspective, Hot Hardware, ExtremeTech, and Anandtech, AMD's new card comes up faster than both a single $450 GeForce GTX 280 as well as two $250 GeForce GTX 260's. Nvidia may steal a win here and there depending on the settings, such as on Crysis, but at higher resolutions and with more image quality details turned on, the AMD card and its 2GB of fast DDR5 memory the Radeon HD 4870 X2 fares better overall.
You won't really see a benefit from the 4870 X2 unless you play games at 1,920x1,200-pixel resolution or higher. That means unless you own a 24-inch or better LCD, you should probably stick to lower-end cards, at least for the moment. You can also double-up AMD's new card in CrossFire mode (AMD's multicard technology, and competitor to Nvidia's SLI), but that would be hard to justify on anything less than a 30-inch display.
Keep in mind that to see any kind of performance gain, both the graphics drivers and the games themselves need to know how to distribute the workload efficiently across multiple graphics chips. AMD's drivers seem to get along well with current games, but we have no guarantee that that will continue to be the case. Of course, you can't exactly wait for new tests for every title that comes out. And based on the performance the Radeon HD 4870 X2 has shown so far, we think it's a safe bet.