NEW YORK ( TheStreet) -- This is an article about the Windows 8 operating system for the PC and tablet, not for the phone.

Windows Phone 8 is a separate discussion, and youcan find my initial opinion about that operating system in "Windows Phone 8 Review: Good, But Not Good Enough."

For several months, I had been very negative on Windows 8 for the PC, but I recently changed my mind. Today I'll explain why.

My impression had been very negative because I'd been playing around with Windows 8 on old, non-touch-screen hardware -- basically Windows 7 laptop and desktop computers that had been upgraded to beta versions of Windows 8 in various stages beginning in February.

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Using Windows 8 on a non-touch PC is a major pain. The new tiles andmenu/touch-points do not lend themselves to a trackpad or mouse. Why? Because you have to hunt from side to side, from corner to corner, and that is an exercise in frustration. Beta-user feedback seemed overwhelmingly negative, confirming my own experience.

But then on Oct. 25 and 26, something happened. For the firsttime, I got to use both desktop/tablet versions of Windows 8 onpurpose-built touch-screen hardware. As it turns out, this made all the difference.

Practically, how does this work? The point here is that as a user,you will be spending most of your time in the major Office apps (Outlook, Word, Excel, PowerPoint), a browser and some other apps you may use such as Skype and Apple's ( AAPL) iTunes. When you use most of these apps, you will not need a touch screen. You will use a trackpad or mouse just as would with Windows 7.

However, when you switch apps -- and, more importantly, when you start thecomputer -- you will find that you prefer to use the touch screen. It's just faster, easier and more logical that way. That's why a touch screen makes all the difference in terms of Windows 8 being an acceptable platform.

In other words, you will be spending 99% of your time in Windows 8using a trackpad/mouse as usual. The problem is that ifthe other 1% is dysfunctional, it completely ruins the experience forthe other 99%. As a result, you should at all cost avoid runningWindows 8 on a non-touch-screen PC. Without a positive 1%, the other 99%will be miserable.

Still, using Windows 8 on a purpose-built touch screen is not necessarily enough to make the operating system a success. Even if that 1% touch-screen experience is as smooth as can be, it comes with a learning curve. The absence of a start button in particular means that you have to figure out basic menu navigation. Learning this may take some people five minutes or less, but for others it could require up to 25 minutes.

Either way, you will be a completely lost and unhappycustomer if you don't have someone show you these basic commands.

There is good news and bad news in this. First, the good news:

Once you have taken the time to learn these basic commands and gestures, I think almost all customers will find that Windows 8 works very well and is a solid improvement over Windows 7. In other words, the learning curve may be steep, but at least it's measured in minutes, not hours.

The bad news: I can see many people buying Windows 8, not investing afew minutes in having someone in the store showing these new basicinterface concepts, and then trying to use it "cold" at home. In that case, initial user reaction may be very negative, causing a major black eye for Microsoft, as well as returned equipment to stores. If this becomes "the story," then Microsoft may be doomed. This was my fear before Oct. 25.

To wit, the all-too-few Microsoft stores are selling only touch-screenPCs now. However, when I walked into Best Buy ( BBY), Fry's and the Sony ( SNE) Store, there were many non-touch-screen Windows 8 PCs. Microsoft has it right, and the people who buy non-touch-screen PCs from these other retailers may cause Microsoft a fatal problem.

There is other good news with Windows 8: It's not all about theinterface and the touch screen. It's also about security andmanageability. Antivirus software is now built in, and wiping/restoring yourPC now takes a few minutes instead of perhaps hours. Thesynchronization across devices and SkyDrive are now as"normal/integrated" as they are for the Google ( GOOG) and Apple ecosystems.

But this is for "regular" Windows 8. not Windows 8 RT.

At least in the near term, Windows 8 RT, including Microsoft's ownhardware (the Surface tablet) is a relative sideshow as far as Iam concerned. Windows RT cannot run Microsoft Outlook or anytraditional PC software such as the Chrome browser or iTunes. Thiscan change over time, but the situation for a buyer today -- andperhaps for many months to come -- is bleak.

Measuring Windows 8 success based on the RT version or the initialSurface tablet should therefore be a mistake. However,Microsoft as a company still faces (reputational) risk from consumerbacklash over RT and the Surface. This needs to be monitoredcarefully.

What Does This Mean for Microsoft?

Microsoft was losing badly in the consumer market. Not one person Iknow has switched from Mac to PC in recent years, whereas many peoplehave done the reverse. A quick walk over to your nearest Starbucks ( SBUX) will confirm this.

Can Windows 8 stem this tide? The potential is definitely there, although I think it will take at least another year for a clear verdict to emerge. Windows 8 now has the stability, security and manageability of the Mac OS and offers something Mac does not: a touch screen.

Then add the further potential if Microsoft can close or meaningfullynarrow the applications gap for the RT platform. RT runs on processors designed by ARM Holdings ( ARMH) and initially manufactured by Nvidia ( NVDA) and Qualcomm ( QCOM), and is therefore both cheaper and power-efficient.

If Microsoft plays things right before Apple also shifts its Mac line to ARM Holdings processors, it could have a trump card.

Apple's advantage remains its superior sales and distribution model,including the lifetime customer support afforded by its almost 500stores. Until Microsoft -- or Google -- matches this, it will be anuphill battle competing with Apple, quite aside from actualproduct merits.

Now there is, of course, another pink elephant in the middle of theroom, which changes this competitive equation in yet anotherdimension, and this is Google's PCs based on the Chrome operating system. These are the Chromebooks (laptops) and Chromeboxes (desktops). If you want the ultimate in simplicity, where there is no need for customer support(stores) because there is nothing causing a customer support event tobegin with, then these Chrome OS PCs are for you.

Both Apple and Microsoft are trying to simplify their PC products, butif you want the ultimate in simplicity, why isn't the 100% pure Webexperience the answer? Google removes any and all need to set up andmanage your PC in any way -- backups, security, synchronization,storage management, application management, updates, etc. -- and makesthe PC experience totally foolproof.

With Windows 8 Microsoft may have stemmed the hemorrhaging of customers in Apple's direction, and it may be able to reverse that trend over time.But both Apple and Microsoft also now have a new threat from the ultimate next-gen product from Google: the $249 laptop, and other models that are sure to emerge from Google in the next few months.

At the time of writing, Wahlman was long AAPL,GOOG, MSFT, NVDA and QCOM.

This article is commentary by an independent contributor, separate from TheStreet's regular news coverage.

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