As an example, they point to the edge-swipe feature that reveals application bars from the bottom of the screen and the charm bar from the right side. "Traditionally, the edges of the screen are where touch sensitivity drops off, and it's a place that hardware manufacturers have traditionally not placed much emphasis on," they write. So on Windows 8 machines, those edges will be made more responsive without sacrificing space that the application can use when the bars are hidden.

Since Windows 7 machines had different design requirements, Microsoft had to do a workaround for screens that are not ideal. "In order to make edge swipe work consistently on Windows 7 PCs, we created a mode where there is a 20-pixel buffer to catch the edge swipe gesture. This allows a majority of PCs to reliably invoke the charms and use Windows 8 effectively," the blog says.

As it says, this may work on a majority of machines, but not flawlessly. On a brand new HP TouchSmart 520 PC tested by Network World, the preview edition sometimes responds the first time with a finger swipe from the left to open up the charm bar, but sometimes it takes two or three swipes. Sometimes it misinterprets the edge swipe for a slide-to-pan swipe which scrolls the screen side to side. So a swipe meant to summon charms can scroll the live-tile screen for the Windows Store, for example.

But Microsoft says it has straightened this out with hardware developers. "There were many challenges here," the blog says, "but we were able to deliver on the promise of Windows 8 PCs that have the ability to trigger the edge swipe without taking any pixels from , and with extremely good edge sensitivity using touch — a promise that benefits developers and users alike."

Other issues the blog acknowledges: