We've been quietly optimizing our software for the last 2 years for the type of hardware we expect to see Windows 8 running on, namely tablets with modest processors and storage space.
Windows 8 features a new API for tablet interaction, called Metro. It is completely unrelated to the desktop. It allows interaction with gesture based interfaces and is based on a clear type structure, with content taking priority over interface "chrome". Metro applications can only be sold through the Microsoft store, and they take a percentage off the top.
Windows 8 also runs desktop software as usual. We are still a desktop application. However touch interaction is fully supported. We've spend most of our Windows 8 time working on performance, however. We want to be "The choice" for tablets.
It's an old adage, but still true. If you want great performace, don't develope on the highest end hardware you can buy. Develope on lowest end stuff you can find. If you run great on that, the high end stuff will be smoking fast.