Nothing wrong here.

This is a single slot 4850 with a stock speed of 650 Mhz and it performs better then a dual slot solution from Nvidia.

Wait untill dual slot overclocked 4850's also become available for comparison. Get that GPU up to 800 Mhz+ on a Zerotherm GPU cooler, and it will cream everything in its price category from Nvidia.

Also, the drivers look to be immature still, and need improving for the 4800's performance.