I'm curious in particular as to how they plan to deal with the UX side of things. I'd go so far as to say that such issues could make or break the entire concept.

There's been no small amount of problems with Windows' inability to adapt to the new wave of high-dpi displays. My partner got a Yoga 2 Pro with the 3200*1800 screen and for example the youtube player controls are almost impossible to interact with in some view modes (even with a mouse pointer). I can see this being similar, in that if the app determines at runtime how to display its controls then there seems to me like there will be issues, for example with reflowing text or image positions to accommodate button size changes.

I mean, the alternative is to have Mattel's My First Computer and have all UX elements touch-size by default but then why even have a high-resolution screen with more precise KBM inputs? I know that I don't really want huge icons on a 4K monitor because i want significant screen real estate.

I think that it's going to be interesting to see how they strike this balance.

Windows universal app is a Windows Runtime (WinRT) application: http://en.wikipedia.org/wiki/Windows_Runtime

WinRT supports multiple UI APIs:

* XAML Framework

* DirectX

* HTML5/JavaScript

Windows universal apps can run on Windows, Windows Phone and Xbox One.

It will be interesting to see if they can pull off the adaptive interface. It would be an incredible achievement if they can do it seamlessly in the first iteration. It's a big enough leap that I'll have to see it before I invest time in it. Nailing a simple To Do list demo would not suffice.

They are including the ability to specify the UI used for the platforms rather than having it done by their framework. I can see why they need to do so to satisfy cautious developers. I hope they're not doing so because the framework will have unacceptable performance in the first release.

Stated goal number 3:

"Maximizing developer investments"

It's hard to think of a worse strategy. "Maximizing return on developer investments" is what Microsoft ought to be doing...

Just a small section about HTML5 in the bottom - thank you very much! Hopefully the unreasonable and unnecessary Win.js push is over.

If they can only be distributed via the Windows app store, I don't really see universal apps taking off.

Which segment of Windows users want the OS to be turned into a walled garden like iOS? Personally, I will never make or use universal apps and I am a developer who actually like Windows.

Oh god, not again