Editors' pick: Originally published May 25.

The unprecedented free Microsoft Windows operating system update offer--to Win 10--is set to expire July 29. Best guesses are that maybe one in four Windows boxes in the U.S. are running Win 10--which means maybe 75% are not. If you are in that latter category, you have a choice to make: to upgrade or not to upgrade?

The free upgrade is a Microsoft first. Historically the Redmond, Wash.-based colossus dinged upgraders upwards of $100 to jump from one version of Windows to the next. Nobody knows exactly why Microsoft made the Win 10 upgrade free, but the prevailing theory is that the company wanted to spur adoption of the latest OS at a time when Microsoft has seen nibbling away at its OS dominance by Apple and also Google (Chrome OS).

It's hard to turn down free, but, frankly, there are reasons some might. OS upgrades always turn some peripherals (from printers to cameras) into junk. Sometimes too the newest Windows is buggy. Often, too, it has run slowly on older computers.

Know if you have been a holdout that there traditionally have been reasons to wait.

Microsoft also has swung a stick to stimulate upgrading. Namely, it has said that by 2020, it will end security updates to Windows 7; by far the most popular Windows version, Windows 7 runs on maybe one in every two computers. That's a long time away indeed, and, by then, the computers it runs on are probably door stoppers anyway. So that is not much of a stick.

So it comes down to this: will the end of "free" goad tens of millions of us into downloading now. Should you?

Listen to Lori Scribner, a PR consultant in San Diego. "I just upgraded late last week," Scribner said. "I had a lot of trepidation about upgrading, mainly because my Toshiba laptop is about 5 years young." She added: "I am happy to report that Win 10 is working well for me. I'm still getting used to it, but really, the UI change isn't all that dramatic. And, even on my older laptop it's working just fine ... for now."

"All in all, Windows 10 upgrade is a great upgrade and we ourselves have upgraded to it," said Trave Harmon, CEO of managed IT provider Triton Technologies in Worcester, Mass. "Excellent platform with very little learning curve."

That is fact: if you have used Win 7 or 8, there is little to learn before flying in Win 10.

That is not to say Harmon has endorsed Win 10 for all his clients. He does not. He divides them into two groups. For those mainly running cloud-based apps, he would "highly recommend" upgrading, said Harmon.

For another group using mission critical software that resides on their computer, hold on, advised Harmon.

That's because there are many reports of software incompatibilities with Windows 10, and at least sometimes there are no ready fixes. And when that means software essential to one's computing life is DOA, it is a very bad outcome. So before upgrading, meticulously check online for reports on how well your key software interacts with Win 10.

Tim Singleton, CEO of Strive Technology Consulting in Boulder, Colo., offered another pre-upgrade test: "What I have heard from my clients and others in the industry is that the upgrade usually goes smoothly with few problems, but on infrequent, but consistent occasions, it goes horribly wrong. If you want to do it, check with your vendor and make sure your model of PC has been tested and approved for use with Windows 10."

But Singleton has another reason besides wariness about upgrades gone bad for going slow with his clients: "We have not seen a lot of improvement in Windows 10 over what users are getting now, so there is no rush to make the switch."

Chew on that and know Singleton is not alone: a lot of geeks view Win 10 as no big improvement over Win 7, an OS known to be stable, secure and powerful.

Pretty much nobody likes Win 8, however--in use on perhaps 12% of computers--so if that's you, go for the free upgrade if significant software or peripheral problems are unlikely.

If you are running Win 7, however, and all is smooth, why rock the boat? Said Singleton: "As a general rule, we are not recommending in-place upgrades for our clients, but instead recommend a slow migration to Windows 10 as computers are replaced."

What that means is, sure, you'll upgrade to Win 10--when you buy a new computer. Until then--do as three in four of us seem to be--and shrug it off. Because why bother?

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.