The ability to pin Modern apps to the desktop taskbar is an interesting piece of cross-environment integration in.1 Update 1. But in experimenting with the RTM version of this update, I've noticed a few additional features I'd not seen before. Here's an interesting example.
If you're familiar with how taskbar pins work in Windows 7 and 8.x, you know that these application buttons can provide jump lists and live previews that show what the underlying app looks like (if running), so you can select the right one before committing.
But with Windows 8.1 Update 1, Microsoft is letting you access Modern apps from the taskbar for the first time. This is actually two features, not one. First, you can optionally elect to show Modern apps—or what Microsoft annoying calls Windows Store apps—on the taskbar. And second, you can arbitrarily pin any Modern app to the taskbar, and this works even if that previous feature is disabled.
Pinned Modern apps provide live previews just like desktop applications, and for the same reason: You can visually preview the app before actually selecting it.
But here's a few things that weren't immediately obvious before.
First, if you're using a Modern app that supports multiple windows—like the Mail app—the preview works like it does for multi-window (or multi-tab) desktop applications: You see a preview of each window.
And second, some Modern apps support embedded active toolbars, just as some desktop applications do. For example, the Xbox Music app uses this toolbar to provide playback controls—similar to how Windows Media Player used to work—so that you can still control your music when you're working from the desktop.
I've not looked at every single Modern app in Windows 8.1 to see what else is available, but these features suggest a deeper attempt at integration between Modern and desktop than was perhaps previously understood. For that majority of Windows users who still stick largely to the desktop, this is good news indeed.
Other features that could be added include progress bar—like when an app is installing through Windows Store, perhaps—and icon overlays, so that an app like Mail could indicate when new emails are available. Since such changes should not require a new OS update, just app updates, I would be surprised if we didn't see a number of such additions throughout the year.