Ok, so it wasn’t the “official” official release, apparently just the leaked official release. But the update went smoothly, and the phone is insanely faster and better than it was before. I found this video guide that shows how to install by downloading the executable to your PC and running it with your phone attached to USB–no need to root your phone to run this update if that’s something that worries you.
The update takes a few minutes to run, and mine was a cinch. Here’s a link to the executable update file that’s referenced in the video.