Sony says the Jelly Bean update "starts right about now," but "as usual, timing & availability may vary by market & carrier." So have patience, and your phone will let you know when it's ready to update. I've contacted the major networks to find out when locked phones will be able to upgrade.
The update puts the waterproof pair just one generation behind the cutting edge of Google's software, with improvements and upgrades also coming to the extra apps and features Sony adds on top of Android.
The Xperia Z1's Smart Social Camera is coming to the Xperia Z Ultra with the update, so you can download camera apps from within the viewfinder as you're snapping. Sony has also updated its own brand apps, such as Messaging, MyXperia, and Smart Connect, as well as the media player apps.
Sony also promises a potentially interesting new feature: Xperia Themes, described as a "unique custom interface experience" that will allow you to download a new look for your phone from online app and game store Sony Select. Sony promises "more on this soon."
Wouldn't it be cool if you had the option to only keep the bits of Sony's added interface you actually wanted, ditching the bloatware or even stripping things right back to stock Android? That's probably wishful thinking though; what's the betting it'll just be different colour skins.
There's no update date for the remaining Xperia phones still waiting for Jelly Bean, other than to promise the upgrade is "right around the corner."
Is it about time new-ish phones like the Zs update to more recent software? Tell me your thoughts in the comments or on our Facebook wall.