I find this a bit hard to believe but according to OCWorkBench the NVIDIA GeForce 9800 GTX will be barely faster than a GeForce 8800 GTS graphics card:
This reference cards comes in a dimension of 4.376x10.5 inch. GPU is clocked at 675MHz while the Shader is at 1685MHz. It has a memory interface of 256 bits wide and incorporates 512MB of 0.8ns GDDR3.
The card supports 3 way SLI and it uses a reference design. Total power requirement for this card would be 168W.
The card supports DX10 and SM4.0.
Initial benchmark shows that this card performs similar to a GeForce 8800GTS. The difference in most games are merely 1 to 2 fps. It is quite disappointing to say for a new card that doesn't show much improvements over the previous 8 generation card.