Note: This post has been updated since its original publication to include details about the official release of version 1903.
"Once burned, twice shy." That's good advice if you're working around a hot stove. It's an equally wise strategy for anyone responsible for administering Windows 10 PCs.
Also: Microsoft kicks off the rollout of the Windows 10 May Update/1903
After the disastrous rollout of Windows 10 version 1809, you should indeed be extremely wary of touching that hot stove. Microsoft had grown cocky after a handful of relatively trouble-free feature updates to Windows 10, and had even bragged about how quickly it was able to roll out those semi-annual feature updates. That hubris caught up with them in late 2018.
Only days after rolling out version 1809 to the public, a pair of data-destroying bugs forced the company to pull the update from its servers. It took more than five weeks before the update was relaunched.
That painful experience inspired Microsoft to rethink its enthusiasm for those every-six-months updates. In the wake of the version 1809 debacle, the company promised major changes in the way it tracks product release, including a renewed focus on product quality.
One of those major changes was a deliberate slowing down of the rollout process for the next feature update. Microsoft's engineering team signed off on the 1903 release, build 18362, in mid-March 2019. Under the previously established norms, that release would have gone to the general public beginning in April. That's not what happened this time around.
Because of the slower rollout process, what would previously have been an April update is now officially the May 2019 Update for Windows 10 (version 1903). And the update itself wasn't released until the end of May, after undergoing additional testing by members of the Windows Insider Program as well as corporate customers and developers with access to early releases of Windows 10.
If you want to upgrade a Windows 10 PC to version 1903, you'll need to use one of the following techniques:
If you attempted a manual update before May 21, you might have encountered the following error message:
That generic message is misleading. During the pre-release period, this upgrade block kicked in if any external storage devices, including USB flash drives and SD cards, were attached to the PC on which Setup was running. (This upgrade block also occurred on PCs with two or more internal hard drives or SSDs.)
The issue is documented in this Microsoft Knowledge Base article: "'This PC can't be upgraded to Windows 10' error on a computer that has a USB device or SD card attached."
The bug, which caused drive letters for secondary drives to be reassigned during Windows 10 Setup, has been resolved in a servicing update for Windows 10, which is applied before the feature update is installed. The May 21 cumulative update, KB4497934, addresses multiple bugs and adds the Download And Install Now option for this feature update. (You should also ensure that you have installed the current servicing stack update for your edition, either by way of Windows Update or manually from this page: "Latest Servicing Stack Updates.")
One of the post-1809 commitments from Microsoft was a dashboard for monitoring the health and stability of each new Windows 10 release. That Windows Release Information dashboard is now live. It contains just about everything you need to know for currently released Windows 10 versions, with dates for when they were made available for their respective servicing channels and their end-of-support dates.
Now that version 1903 (build 18362.116) has been released to the general public, its details have been added to this list, under the Semi-Annual Channel (Targeted) servicing option. Using the links on the left side of that page, you can track known issues, including the status of upgrade blocks. As of release date, May 21, 2019, the list of known issues (with status listed as "investigating") includes three items, with another nine items on the list checked off as "mitigated."
Even though Microsoft is continuing to roll out the version 1903 update slowly, I recommend caution. You can monitor that release health dashboard to identify bugs that might affect PCs you manage. For business customers, consider waiting until Microsoft has declared version 1903 ready for widespread deployment. When that happens, you'll see a new line on the dashboard for the Semi-Annual Channel servicing option.
And even that milestone doesn't mean you need to rush into an update. Consumers and small businesses have 18 months from the release of a feature update before they're required to install an update. For version 1803, the end-of-service date is November 12, 2019; for version 1809, the date is May 12, 2020.
In theory, for any PCs you manage that are running version version 1803 or later, you have at least six months to test version 1903 before you have to begin making upgrade plans. If so, you might be surprised. In today's blog post announcing the availability of version 1903, Microsoft offered more details about how it will approach feature updates as the end of service date approaches:
For Windows 10 devices that are at, or within several months of reaching, end of service, Windows Update will automatically initiate a feature update.... The Windows 10 April 2018 Update (Windows 10, version 1803) will reach end of service on November 12, 2019 for Home and Pro editions. Starting this June, we will begin updating devices running the April 2018 Update and earlier versions of Windows 10.... [emphasis added]
If you're uncomfortable with the possibility that your older version of Windows 10 will receive the version 1903 update in the next few weeks, your best bet is to update to version 1809 as soon as possible.
On machines running Enterprise or Education editions, you have 30 months of support for so-called H2 versions released in the second half of each year. If you manage Enterprise or Education deployments editions, version 1803 does not reach end of service until November 10, 2020, and the end-of-support date for version 1809 update is May 11, 2021. (Pay special attention to those dates; because version 1809 is an H2 release, its end-of support date is six months later than version 1903.)