I would have to agree. Overall, the HD 6850 is slower than the HD 5850 (the next card up from the HD 5770). However, it does have a better DX11 engine so in DX11 games the HD 6850 should perform a little better than the HD 5850. But in DX9 and Dx10 games, the HD 6850 a little worse than the HD 5850.
The overall raw performance of the HD 6870 is better than the HD 5850 in all DX9, DX10, and DX11 games which makes a more ideal upgrade than the HD 6850.