Microsoft has finalized the first major update to Windows 8.1, which is internally called Windows 8.1 Update 1, in keeping with the update naming conventions for Windows Phone. Externally, Microsoft has referred to this update as the "Windows 8.1 Spring Update" and even more simply as "Windows 8.1 Update," so the messaging is about as clear as ever.

News of the Windows 8.1 Update 1 RTM (release to manufacturing) comes courtesy of Mary Jo Foley, who has impeccable sources, as well as the Russian Windows leaker WZOR.

As readers of this site know, Windows 8.1 Update 1 offers several improvements to the core OS, including most controversially some mouse-based context menus in the Start experience that are inconsistent with how the mouse works in other Modern experiences in the OS. (This triggered my What the Heck is Happening to Windows? commentary, in which I question the soundness of this change.)

What's oddest about this update, perhaps, is Microsoft's continued silence about its very existence. The firm has only mentioned it once, officially.

In mid-February, outgoing Microsoft marketing chief Tami Reller referenced some Update 1 features—the smaller disk and memory footprint that will only be available via new devices from hardware makers, for example—but never actually discussed the update explicitly.

Last week at Mobile World Congress, however, Microsoft's Joe Belfiore finally discussed the update, both in a blog post an in a press event.

"When the Windows team revised the UI for Windows 8, they had a big focus on touch," he said at the press event. "They wanted Windows devices to work in this new, highly intuitive touch-based model. But for that to fully pay off, you need touch devices. Users of Windows 8 on touch devices are more satisfied than users with Windows 7. However, it's also the case that users of Windows 8 on non-touch devices were, in general, a little less satisfied with Windows 8 and its UI compared to Windows 7. So the team, believing in the direction we had taken with touch said, man, we would like to go back and address some of these customer satisfaction issues."

Belfiore then announced "a new update, coming this Spring for Windows 8.1" that focuses on three specific things:

Improvements to the non-touch experience. This is the context menu on Start stuff that I think is so awful (because it's inconsistent) and it "follows the customer satisfaction data" that Belfiore mentioned at the press event.

More hardware options. "We knew that we needed to give our [hardware maker] partners more flexibility, in particular to reach low price points." I wrote about this previous to MWC in Report: Microsoft to Drop Windows Licensing Fees for Low-End Devices. Two things are changing: the price of licensing Windows, where devices that cost less than $250 will have much cheaper licensing, and the "flexibility" of licensing Windows, where hardware makers who do play in that low-end pricing category no longer need to partake in the Windows logo program.

Improved compatibility for education and enterprise. Customers in these segments "are looking for improved management and better compatibility with legacy web sites.

In addition to these changes, Belfiore said that Windows 8.1 Update 1 will include more discoverable Search, Power and Settings on the Start screen, and easy (Modern) app launching and switching from the desktop-based taskbar. It will now support a new low-end range of hardware—key for hitting those price points—where devices have just 1 GB of RAM and 16 GB of onboard storage, which is pretty much where the Android and iOS devices start, of course. And Internet Explorer 11 is being updated with an IE 8 compatibility mode so that recalcitrant enterprises can upgrade.

Nothing we didn't already know, in other words.

As for availability, I previously and exclusively revealed on Twitter than Microsoft plans to deliver Windows 8.1 Update 1 to MSDN subscribers on April 2 and then via Windows Update on April 8. The Build conference, probably not coincidentally, is scheduled for April 2-4 in San Francisco. At that show, Microsoft is expected to discuss the future of Windows, and its plans to integrate Windows and Windows Phone.