With the Volari Duo V8 performing around the same levels of a Radeon 9800 256MB on 3Dmark03 it is a bit dissapointing because it seems that they needed the dual GPUs in order to compete. But then again this is early product hardware and drivers, although I'd highly doubt XGI improving performance as drastically as ATI or nVidia could do if they were in the same boat. That and we probably won't see the card available until we see other refreshes such as the 9800XT so it might not ever stand out at all.
It'll also be really interesting to see the product in action in real world senarios and not just synthetic benchies. Could have a good lead over 9800/5900 in real games or on the flipside it could have a real lack. What really will be interesting to see is it's performance in a game such as HL2.
If their hardware isn't as incompatible with DX9 paths on HL2 as nVidia hardware is (hope that valve honostly did not "work with" ATI...) then it would be interesting to see the performance. If a single GPU V8 can possibly compare to a 5600/9600 and noting how well the 9600 does in HL2, a duo V8 could be promising considering how GPU hungry HL2 as memory bandwidth and efficient management thereof is seemingly ahead of the curve. But that's also another concern. ATI and nVidia have seemingly gone through great strides with being able to run games high res with AA and AF settings not just a dream. Who knows, the XGI's sheer bandwidth and/or bandwidth management might not be so hot.