While I agree with the above posts, that *currently* nothing saturates a x16 slot let alone a 2.0 x16 slot, no ones explained what the actual diffrence is. 2.0 x16 is double, thats DOUBLE the speed of a 1.0 x16 slot.
To quote Wikipedia: The first-generation PCIe transfers data at a 2.5 GT/s (
gigatransfer per second) signaling rate per lane. PCIe version 2.0 provides an increase in the signaling rate to 5 GT/s per lane.