FUD Zilla points out the reason why few netbook builders are adopting the 1.86GHz Atom processors, it's because these chips are too expensive. It's not a little price bump, the 1.86Ghz Atom costs around twice as much as its 1.6GHz counterparts.
Currently the Z530, a 1.6GHz Atom with 512KB cache, FSB 533 and 45nm development process sells for $65, and the N270, a CPU with the same spec, is selling for $44 and is very popular among netbook manufacturers.
Z540, a 1.86GHz Atom with 512KB cache and FSB 533 is selling for a whopping $135 and the price is the main reason why this CPU is not widely accepted. We don’t understand why would Intel like to keep this SKU at such a high price, but probably yields at 1.86GHz are not as good as with 1.6GHz.