No, video cards these days are not even using up the full 16 lanes provided in the Pci-Express 1.0 slots. So you won't notice a difference between using pci e 1.0 and 2.0, at least not a very noticeable one.
I think the only real benefit would be not having to use the power connector as I believe the 2.0 slot provide enough power to the card. I believe that is what I read somewhere but don't quote me on it as I have nto tried myself.
Still need the power connector, PCI-E 2.0 consumes more power too because it runs at twice the frequency of PCI-E 1.x.
It its much more scalable than 1.x but we wont see any real benefits unless your MB has 4 PCI-E slots which would be able to run at 8X speed (more than enough). PCI-E 2.0 is basically PCI-E 32X on a 16X design.