Earlier, we heard that Intel's Haswell CPUs might have problems with certain less expensive or older power supplies, because the Haswell CPUs would be too efficient for them. A number of manufacturers have already released the lists with compatible power supplies; SeaSonic now joins them.
SeaSonic's lineup of power supplies that support the Haswell CPUs include the 80+ Gold lineup and the 80+ Platinum lineup. The ultra-efficient Platinum series is supported, as are the units without fans. The 80+ Bronze lineup, which includes the M12II 750 W and 850 W units, are also compatible, along with the X Series.
I think most older PSUs will work fine with Haswell systems. The power draw of system fans, and other hardware will keep them steady enough probably. Don't buy a new PSU unless you need to. I really think it's completely marketing. Capacitors on the motherboard can buffer the reference voltage to keep voltage where it should be as the cores go in and out of their sleep states.
My money is that this is all a PR stunt to sell power supplies.
I see that the M12II is in the list, but not the previous M12 (which is what I'm current using). I'm not going to lose any sleep over this. I'm more worried about low stock when Haswell launches.