Funny how there are so many of you that are willing to start bashing nVidia so quickly.
The 7900 GX2(7950GX2) was not to combat the x1950XTX, it was to experiment with Quad-SLI. The 7900GTX did perfectly fine competing with the x1950XTX, it wasn't quite as fast, but it did the job, and there were overclocked version that were on part with the x1950XTX.
This isn't simply a thrown together solution to compete with the 3870 X2, I wouldn't be surprised if there was just as much planning in this card as the 3870 X2. This isn't he first time nVidia has done it this way, and it worked in the past(with the exception of poor driver support) so why change the way it is done? Why manufacture one extremely complicated PCB(and the 3870 X2's PCB is extremely complicated) when you can manufacture 2 PCBs that aren't that much more compicated than a normal video card?
Besides that, the 3870 X2 was just a solution to compete with nVidia's 8800GTS(G92) and 8800 Ultra. So making the argument that the 7950GX2 was just thrown together to compete with the x1950XTX and making a big deal out of the fact that nVidia could get a single GPU to compete with the x1950XTX is kind of hypocritical since that is exactly the problem ATI is facing right now.
The move to use 2 PCBs has its advantages. One major one I can see is that if oen of the PCBs is bad, it is cheaper for nVidia to simply replace that one instead of replacing the whole card.
Yes, there are advantages to both designs. I'm not saying one is better than the other. ATI chose thier method and nVidia stuck with the method that has worked for them in the past. By the way, which one of the two has had a dual GPU card that was actually successfull before? And what design did it use? Yeah, I can see why sticking with that design was such a bad move.