Windows 8 (its codename, Microsoft hastens to remind us) has been shown to the world for the first time, and it’s the most radical shake-up of the Windows UI perhaps since the taskbar and the first Start Menu showed up in the 1994 pre-releases of Windows 95.

Tentatively set for release some time next year (so we can expect a public beta relatively soon, providing it doesn’t become the next Longhorn) the new Windows doesn’t appear to be too dissimilar underneath to the old one: we can safely expect it’ll have Windows NT 6.2 (or 7.0, whatever they decide to number it) pulling the strings in the kernel area. Windows 8 introduces support for the ARM processor architecture, and the “traditional” Explorer-based desktop still exists. More on that later.

The primary shocker with Windows 8 is the brand new user interface, which is a more colourful and larger form-factor incarnation of the Metro interface from Windows Phone 7. Unlike previous versions of Windows, which crudely grafted janky multi-touch on to controls designed to be driven by a keyboard and mouse, Metro is designed from the very beginning to be finger-friendly.

Of course, given that most PCs floating around today still use a hardware keyboard and a discrete pointing device, the Windows 8 version of Metro is also theoretically meant to be nice to drive using a keyboard-and-mouse arrangement.

This means that the new Start Menu bears more than a passing resemblance to WP7′s home screen, with lovely colourful tiles and bold typography, making full use of the available screen space. This is an abrupt departure from the old WIMP (Windows, Icons, Menus and Points) model used by all Windows versions prior to Windows 8: there’s no window title, and nothing to distract you in the Start menu.

Those of us who like multitasking will be pleased to hear that Microsoft has devised an elegant solution for running apps side-by-side in landscape mode. It’s a simple tiling window manager that isn’t all that different to what shipped with Windows 1.0 in 1985 (when Microsoft were fighting off look-and-feel litigation from a then-Jobsless Apple Computer, and were hence forbidden from allowing overlapping windows.) The important thing to note here is that there is no desktop background, no window titles: you are literally playing with two tiles. (This has only been demonstrated in a side-by-side arrangement with the display in landscape mode thus far, although it is entirely likely that it’ll support portrait mode and more complex tiling come release time.)

Of course, old apps won’t magically adjust to the new form factor, and for this, Microsoft claims that the new, full-screen, web-connected apps will be written in HTML5, CSS3 and JavaScript. This is unusually progressive from Microsoft, and it remains to be seen exactly how much of the new apps will be written in the HTML, CSS and JS environment (which I shall refer to simply as HTML5 from now on for brevity’s sake.) If it isn’t simply the UIs that will need to be rewritten to take advantage of the UI, and the whole app will need to be in HTML5, this is an extremely risky move. To get all major apps to fully transition to the touch-friendly UI could take many years. That said, given the massive shift in UI paradigm that Windows 8 will bring, now is as good a time as any to start it.

Legacy window-based apps will continue to be supported, as the old Explorer-powered desktop is hidden behind one of the tiles. The desktop can be tiled with new touchy apps, although this does seem like a fudge: if anything, this will simply be a “ghetto” for apps that haven’t haven’t been updated to work with the new tiled UI.

The thing to remember is that unlike the iOS in use on the iPad, Windows 8 is one-size-fits-all: it’s still a full-featured PC operating system, like previous releases of Windows and Mac OS X, but its UI has been fully redesigned to account for the increase in capacitative touch screens. Whether this approach pays off is yet to be seen.

Other points of note include a new version of Explorer in the desktop ghetto, which now has a Ribbon, making it look uncomfortably like the Windows 3.11 File Manager in the process, edge-swiping and a new task switching method for touch screens which involves dragging in from the left-hand edge. This process of paging through every single window currently open seems like it could get laborious pretty quickly, so I hope Microsoft pay some more attention to this in future. It’s also worth noting that there is also a Metro file manager, which provides access to the file system from the new Windows 8 apps (so none of the app-is-a-silo nonsense that has blighted the iOS.)

Switching to Metro is a bold design move for Microsoft, but I feel it’s one that will ultimately pay off. It certainly looks the part: something I’ve noticed about both the WP7 and Windows 8 versions of Metro is that it bears a striking resemblance to LCARS from the Star Trek series and films of the 80s and 90s. It looks strikingly modern in comparison to the iOS, which is starting to feel rather too glassy and gradienty for some.

I’ve been impressed enough by WP7 to look to acquiring a HTC 7 Mozart in the near future (and when I do, rest assured, I’ll be posting a review here.) If Microsoft can produce a similarly well-thought-out system for desktops and tablets, it’ll be an exciting future for home computing from all fronts. I’m certainly looking forward to playing with the public beta of Windows 8 if, and when, it shows up.

Microsoft are hoping to release it some time next year. We can only hope this isn’t going to turn into another Longhorn debarcle.

NB: The pictures used in this article are courtesy of Microsoft. You might try to re-use them, but I cannot guarantee that you will not be assimilated as a consequence.