Microsoft launched Windows 8 in October 2012 and so far Windows 8 and Windows RT (the mobile OS) have done really well. Windows 8 has seen huge sales since the first month of its launch and this number is bound to increase. Forecasts are that Microsoft will ship 50-100 million Windows devices each quarter.
Investing into getting your Windows 8 and Windows RT apps# out NOW will be the right decision, given the enormous advantage you will get over competition.
Unlike the iOS and Android stores, where the sheer number of apps buries any new ones, the Windows RT/Window 8 market is relatively new, with less apps and low competition.
The Windows 8 app market is going to be large and yet has the opportunity of the early iPhone days. Get your apps developed/ported to Windows Store today and get the advantage that early iOS apps got.
If you have a idea in mind for your app, consider these Windows Store design guidelines:
Flattened navigation hierarchy - Use App bars instead of navigation and tab bars. App bars are hidden by default and appear when people swipe a finger from the bottom or top edge of the screen. So consider using a flattened navigation hierarchy so that more content is accessible via the app's main screen, eliminating the need for navigation.
Grid layout - Like Twitter Bootstrap, it uses grid layout which makes it easy to scale the design for different resolution screens. Use their adaptive layout for different orientation and screen sizes from a small tablet screen, to a medium laptop screen, and all the way up to a large desktop screen.
Direct manipulation - Use "Semantic Zoom" for direct manipulation whenever possible (like in photo album, app list, or address book). Semantic Zoom uses two modes of zoom levels for organizing the content: high - level mode that displays items in groups and low level mode that is used to display items in a flat structure as if it is displaying the items from a group. The Semantic Zoom interaction is performed with the pinch and stretch gesture.
UseFlipView” to flip through views in an app or through a collection of items, like photos in a photo album, one at a time.
Also consider looking below links from Windows Store design guidelines