I can't remember who pointed me towards these, but the example UWP applications in the linked page, while not downloadable by the generic public, are well worth glancing over (in video form, at least) since they give a real insight into how UWP applications adapt their UI according to the form factor they're being run on. And, for developers, you can click through to the source 'how to build it' posts, perhaps re-using code for your own projects.

From the Windows blog post:

The UWP App Experiences are beautiful, cross-device, feature-rich and functional app samples built to demonstrate realistic app scenarios on the UWP platform across PC, Tablet, Xbox and more. Besides being open source on GitHub, each sample is accompanied by at least one blog post and short overview video, and will be published on the Windows Store in the upcoming month to provide easier access for developers.....

...Fourth Coffee is a news app that works across desktop, phone, and Xbox One, and offers a premium experience that takes advantage of each device’s strengths including tailored UI for each input modality such as controller on Xbox, touch on tablet and mouse on Desktop.

And so on, with numerous examples of UWP applications looking pretty and adapting to form factors. I've embedded a few of the demo videos (meant for developers) below, for convenience.

Universal Windows Platform applications are critical to Windows 10 - most of the core first party applications are now UWPs, meaning that they work whether the device has an ARM or Intel chipset and whether the device is a phone or laptop or Xbox (etc.) And, as you'll have seen on AAWP, more and more third party UWPs are arriving every week - and some of them are beautifully done.

Even Microsoft's declared intention to start moving part of the PC scene to ARM (to match the phones) won't affect developers for the most part as long as their UWP applications conform to the guidelines. It's something of a utopian vision that Microsoft is crafting and implementing before our eyes. And yes, that sounds a little too gushing, but temper all this by timescales that span years, so don't get too excited.

Anyway, interesting stuff. Here are a couple of the videos for your enjoyment and interest. They're all short, meant as teasers for developers to click through and start coding: