The Radeon HD 4850 X2 is essentially two Radeon HD 4850s in CrossFire mode on a single card, and it will beat the similarly priced GeForce GTX 260 Core 216 and more expensive GeForce GTX 280 hands down. It will even put the hurt on the new, more expensive GeForce GTX 285.
We're still quite pleased that the Radeon HD 4850 X2 can now be found on Newegg for $260. At this price, it's the same price as two Radeon 4850 cards, but is more accessible in that it will work with any PCI express motherboard. In either case, that's a lot of performance for the admission price.