We all know x8 bandwidth has yet to be saturated by even 6990s at 2560x1600. However, this might not be the case at Eyefinity resolutions. These benchmarks show that even with 480s in SLI there are notable differences between x16/x16 and x8/x8. Now that Toms has the monitors, and a 7970 in hand, I think once a second card is obtained that the review should benchmark on both a LGA1155 platform which is mainstream gaming today, and LGA2011 which while isn't mainstream yet, is the natural progression for multi-card setups.
It's been over a year (that I've found) that there has been a definitive test of x8 vs x16 bandwidth concerns while dealing with multi-monitor resolutions. There's no better time than now considering the introduction of new architecture. This could also be a lead in to the PCI-e 3.0 standard that is introduced by not only the 7970 but LGA2011 and supported by its corresponding (uncertified due to lack of testable gpus) cpus.
As of right now there is little reason for gamers to adopt X79. If it can be shown that PCI-e 3.0 and (mostly) the 40 pci-e lanes that are native to X79 are a benefit to ultra-resolution gaming then it's a worth looking into in my opinion.