Microsoft showed off the first demos of Windows 8 at the D9 conference and on its blog today. In its current form, it’s basically a blown-up version of the Metro user interface that also graces Microsoft’s Windows Phone operating system. That’s not a bad thing at all, actually. With its live tiles, the Metro UI provides users with one of the most information-dense “desktops” around without giving up aesthetics for clutter.

There are lots of novel aspects to the new interface in the world of Windows. The fact that apps default to running in full-screen mode, for example, clearly shows that this interface was designed for touch devices. Everything from the task switcher to the way multiple apps can run side-by-side screams tablet. If you haven’t done so yet, take a look at Microsoft’s introduction to the new UI below.

Windows 8 UI: Just a Shell on Top of the Windows 7 UI?

I’ve always enjoyed the Metro UI, so I’m glad Microsoft is sticking with this idea. But did you notice what happens around 3 minutes into the video? The Metro UI disappears the moment a legacy, non-Windows 8 app is opened and all you’re left with is the regular Windows 7 interface, including the Start button, the regular Explorer file manager and the basic Excel interface.

I can’t help but think that once again, Microsoft’s need to support legacy software is going to hold Windows 8 back. Microsoft should be commended for its “touch first” approach to building the UI and telling developers to do the same thing, but underneath the glossy new interface lurks a regular desktop interface that’s meant to be used with a mouse and keyboard and that isn’t anywhere close to touch-friendly. Indeed, this concept turns the Windows 8 UI – at least in the eyes of a regular user – into little else but a shell that sits on top of Windows 7.

On the desktop, you don’t really need the new UI to do your work, so most people will likely just opt for the traditional Windows interface. On a tablet, having to deal with these legacy tools like the Explorer, simply ruins the experience.

Let’s be clear, though: I’m quite impressed by what Microsoft showed today and it’s still a long time before Windows 8 will go into production, so we need to take today’s demo with a grain of salt as things will likely change before the final master copy is compiled. I am afraid, though, that the Windows 8 UI will be fine for the desktop (because you’ll be able to route around it), but that this combination won’t make for a satisfying tablet/touch experience.

What do you think? Let us know in the comments.