Metro apps: Best for consumption
Metro's interface isn't its only facet. The way apps work under Metro is also significant -- so much so that Microsoft engineered an app-development platform and design language around it, WinRT. The Metro model works best for apps geared toward information consumption -- what some have called "lean-back mode" -- or where interaction is reduced to a few simple gestures. A Metro video playback app is going to be more useful than, say, a Metro-based text editor. On the other hand, a Metro Twitter client might be a good compromise; you'd still need to type, but not as much. Not surprisingly, most Metro apps thus far are content consumption apps or apps designed for simple interactivity, such as games.