A recent reader survey on TweakTown polled 5021 readers about what they think is the most important new motherboard technology. USB 3.0 won with a convincing 29%. CPU upgradeability and SATA 3.0 (6Gbps) followed in 2nd and 3rd place with 23% and 22% respectively.
Another high scoring item was overclockability with 12%. The full results can be found here.