PCI-e 2.0 has theoretically twice the bandwidth of PCI-e 1.1. It doesn't quite work out to double, so PCI-e 1.1 x16 is better than PCI-e 2.0 x8. GTX260's don't come close to saturating PCI-e 1.1 x16's bandwidth, don't worry. You only need to start thinking about it when you get into the 4870x2 and GTX295.