What is the performance loss of using a pci-e x16 2.0 video card on a pci-e x16 slot?

I was planning on getting this video card http://ping.fm/z0nef and i wanted to know how much of a performance loss would be noticeable on a pci-e x16 video card, because that is all I have on my mobo. http://bit.ly/mKsnMd