Windows 7 is considerably better than Vista, IMO, yes.

I very much doubt there are any known issues with the 8800 GT.
The 8800 series was (is) very popular and a whole lot of people got them. It stands to reason if they got a lot of complaints, alot of those people would be using 8800's. Law of averages and all.

As I already said, sometimes Nvidia drivers aren't that great, and they had a problem with the 8800s for a while, when they were new. Just like they're having issues with the GTX 200.x series now.

You can buy your 8800 GT and rest assured that any problems you may have with it can be ironed out easily enough. I very much doubt Poser can distinguish one model from another. It sees the drivers, not the hardware, and the nvidia 8800 line is rock solid, reliable, and has nothing about it to inherently cause Poser issues.

One thing about tech people... sometimes they just tell you what they think you want to hear. Sometimes it's easier that way.