Surge,
It wasnt until recently that the nvidia driver for Vista offered SLi. Their first batch came in Jan. Those were buggy as could be. They have since modified them but they still do not work as well as they do in XP.
I know several people that have many, many issues trying to run SLi in Vista. Not jsut 64 Bit either. But 32 Bit as well.
It could be that i am wrong and the newer sets do run SLi easily. But from my talks with everyone i know that runs SLi in Vista they complain of drivers crashes almost daily. Along with BSOD's on a regular basis. So while SLi may work. I have not seen it stable. Many times people have removed a card or disabled SLi to use Vista.
I have also seen and heard that Vista doesnt support 2 different types of video cards as well. Some of this may be outdated but as of at least June i know that many of these issues were still present on many machines. Espically gamers.
I have heard that 64 Bit Vista is much better than 32 Bit and is recommended by many of my friends. So it could work. I jsut caution people cause it may not work as they expect and give issues. Vista already has a bad rep that it doesnt deserve from manufacturer's not getting things done right for it. Last thing we need is a influx of more peopel coming by and complaining that Vista doesnt run their SLi like they want.
I amy be wrong. But i am going by my experience with SLi and VIsta. It could be that those machines are running a modded driver as i haev seen and heard that these are better than the default nVidia ones. So that could be a very good option.
Cheers,
Mak