It is clear that the resolution of 2560x1600 pixels is a summit Nvidia’s single-PCB solutions are yet to conquer. This task lies with the upcoming dual-processor GeForce GTX 295. The current flagship GeForce GTX 280 ensures good speed in some games but is unable to compete with the Radeon HD 4850 X2. The Sapphire HD 4850 X2 is about 27% faster than the Leadtek WinFast GTX 280 on average but there were problems with bottom speed in Far Cry and the second GPU did not work in Dead Space.
ATI Radeon HD 4850 X2 vs. Nvidia GeForce GTX 280: Decisive Battle (page 18) - X-bit labs