Hype. All of it. People wanted better performance in Benchmarks over 975 and so tried Nvidia 680 or ATI RD600. Which chipset has the greatest performance/stability? The good old 975 seems to be the best overall. Less bugs, lower temps, better reliability...not surprising that Intel make the best chipsets for their own CPUs.
Both the Nvidia and AMD chipsets allow for higher FSB at the cost of RAM performance and higher chipset temps and stability. I'm not saying all 975 boards are perfect but a good 975 board with RAM running tight timings @ 800Mhz is better, or equivelant to, other chipsets running RAM at 1200Mhz.
Stability and temps are everything to most home users. Generally the best 975 boards are cheaper and more stable out of the box than the competition boards.