[dimentionalrift]

There is a problem when trying to find significant differences between the 8800Ultra and the 9800gx2 due to several simple factors:
1) When the CPU isn't very powerful (Intel Core2Duo, AMD athlon 64 X2,...), a lot of the raw potential of the GPU is stripped away inorder to balance the shortage in CPU power.
2) Due to the much larger width of the 9800gx2, you can only fit up to 2 cards on a single motherboard, while the 8800Ultras lighter and slightly denser design allows up to 3 GPUs, which equals a lot more potential (2 heads are good, but 3 are even better).
3) The GPU strength/GPU energy usage ratio of the 9800gx2 is lower than that of the 8800Ultra.

HOWEVER, once you put a strong enough CPU (for example the Intel Core2Quad Extreme QX9775-4.0GHz), the card can unleash its inner strength. With such a CPU and about 4GB of DDR3 SDRAM memory, 2 9800gx2 will outperform even a triple 8800Ultra combination in games like Crysis and UT3 if you put all the settings to maximum and a res of 1280x1024 or maybe even as far as 1900x1200.

A more imporatnt note is the fact that the 9800 cards are only a transition stage for Nvidia, just enough juice to keep the company's stocks running until they release the 9900 cards later this year. Expext monstrous specs from them...I would.