Windows 8: Microsoft’s greatest comeback ever — or its last hurrah?

Today is the day Microsoft begins to show whether it can repel the direct frontal assault on its PC hegemony made by the iPad (and, to a lesser extent, Android) or follow Wang, DEC, and others into the recycling bin of computing history.

It’s a long road, and the official reveal of the new Windows 8 tablet/desktop platform at Microsoft’s Build developers conference is hardly the final word. Win8 is probably a year away from getting into customers’ hands, where the rubber really meets the road. Remember the cardinal rule of Microsoft: Everything always looks good in the demo — except when the demo crashes.

Still, we know more about Win8 today than we did yesterday — enough at least to make contradictory predictions about it and Microsoft’s future. Here are five reasons why Windows 8 will resurrect the giant’s reputation and make it relevant again (followed by five reasons it won’t).

1. Vista’s long shadow. Microsoft seems to have been sincerely humbled by the Vista debacle, one of the few times it has had to publicly admit defeat. Windows 7 — a surprisingly elegant, relatively trouble-free OS — was the result. Steve Sinofsky was the architect of both 7 and 8, and one thing he has learned is to not overpromise and underdeliver.

2. It’s not an iPad. Enterprises are desperate for an alternative to Apple tablets, but they’re equally wary of Android. Microsoft’s greatest strengths — and most fiercely loyal customers — reside in the enterprise, where Apple has comparatively few friends. The bar is actually lower; Microsoft doesn’t have to outinnovate Apple. It just has to enable mobile devices that can be managed as easily and securely as a BlackBerry.

3. Roll your own OS. At least some builds of Win 8 will come with Hyper-V, allowing users to run the OS of their choice inside a virtual window — thus, easing migration concerns and enabling legacy apps. Naturally, how well this will work and what hardware resources it will require remain to be seen.

4. Developers, developers, developers. The iTunes App Store and its brilliant marketing are what really separates Apple from the tablet herd. With support for older development languages as well as the likes of HTML5, Windows 8 will have at its disposal an army of developers who don’t have to start from scratch to bridge the app gap.

5. It’s Microsoft, dammit. Like zombies, every time you think Microsoft is dead, it rises up again and makes another lunge. Imitation, not innovation, is this company’s strong suit. It can afford to hang around and wait for everyone else to fail; given the HP TouchPad’s spectacular flameout and RIM’s shaky PlayBook strategy, Microsoft might not have to wait long.

So Win8 is a dead-cinch success, right? Not so fast, kemosabe. Here are five reasons why it might sink — and take Microsoft along with it.

1. Dessert topping or floor wax? Microsoft is trying to mash up two disparate interfaces — traditional mouse/keyboard and touch — in one OS. Tablets are notoriously bad at keyboard input, while PCs have yet to demonstrate more than minimal competence with touchscreens. Win8 will have to handle both equally well on both mobile and desktop devices to win acceptance.

2. Ribbons and Tiles and Metro, oh my! Win8 schizophrenia extends to software, mixing Windows Phone 7-style “live tiles” with the Office 2010 ribbon toolbar. Old Office hands say the ribbon makes them more productive, but newbies tend to run screaming in the other direction. Users will have to get comfortable with tiles that can be either live data streams, apps, or files, depending on where they are. Enterprises looking to make the Win8 plunge may be forced to plump up their training budgets.

3. Hardware gone wild. Apple, of course, controls everything inside its ecosystem, while Google now owns Motorola Mobility. But Microsoft still has to rely on hardware OEMs to bring the sizzle to its OS steak. Particularly with tablets, even a small difference in weight, thickness, or battery life can make a huge difference in the marketplace (see HP TouchPad, above).

4. Security, security, security. In the Decade of the Hacker, everything had better be locked down tight. Microsoft is much better about security than it used to be, but then again, it was awful. By virtue of market size alone, Windows 8 will have crosshairs on its back; Internet Explorer 10 needs to be more secure than Chrome, Firefox, or Safari for Microsoft to have a chance.

5. It’s Microsoft, dammit. Will Win8 come in 2 SKUs or 12? Will users have to jump through hoops to document they own the copies they paid for? How many times has Microsoft shot itself in its collective feet over the years — and how much more patience will the market have? Even a zombie will die if you cut off its head. Windows 8 may be Microsoft’s last chance to sink its teeth into the action.

This article, “Windows 8: Microsoft’s greatest comeback ever — or its last hurrah?,” was originally published at InfoWorld.com. Get the first word on what the important tech news really means with the InfoWorld Tech Watch blog. For the latest business technology news, follow InfoWorld.com on Twitter.