On Monday, Microsoft unleashed a massive new update for intrepid Windows Phone 8 users: A free upgrade to Windows Phone 8.1. Although it's tagged as a developer preview, this release actually represents the RTM, or final version of Windows Phone 8.1, and virtually anyone with a Windows Phone 8 handset can get it now.

"Introduced last October, the Windows Phone Preview program gives our developer community access to prerelease builds of Windows Phone updates before the operating system updates are made generally available to consumers," Microsoft's Cliff Simpkins writes in a post to the Building Apps for Windows blog. "We make these updates available to you to enable on-device testing, and to enable you to build and test platform capabilities not present in the emulator."

But here's the catch: anyone with a Windows Phone 8 handset that has been previously upgraded to Update 2, which shipped in mid-2013, can get this update now, for free. When the public upgrades hit over the summer, they'll be automatically upgraded to whatever firmware updates and other software that are provided by their handset maker and wireless carrier.

Is it risky to do so? Any upgrade is potentially risky, of course. But if previous developer preview and publicly-released Windows Phone 8 upgrades have done anything, it's instill a sense of confidence. Millions of people have installed these updates over the past several months, and there have been no widespread issues to date.

Interested in upgrading immediately? You can learn how to get Windows Phone 8.1 today by checking out my article "Get Windows Phone 8.1 as Soon as Possible."

If you're a Windows Phone enthusiast, it's absolutely worth the effort. Despite the version number—which was chosen to bring the system in line with the current version of Windows for PCs and tablets—Windows Phone 8.1 is a major new release, with several big bucket features like the voice-enabled Cortana digital assistant and the Action Center notification hub, as well as a ton of other smaller but useful new features. You can learn more about Windows Phone 8.1 in my new Windows Phone 8.1 Review and previous Windows Phone 8.1 Preview.

If you can wait that long, Windows Phone 8.1 will roll out on new phones over the next several weeks and to existing Windows Phone 8 handsets by the summer, Microsoft says.