It's a good time to be a Samsung owner, at least if you've got some recent hardware. After beginning an extensive campaign of Android 4.3 updates for US models of the Galaxy SIII, S4, and Note II (likely motivated by the Galaxy Gear compatibility it provides), Samsung is now starting to update the massively popular international SIII model, the GT-I9300. According to SamMobile, Irish S III owners on Vodafone are the first to get the update, with no other regions reporting in at the moment.
The Jelly Bean 4.3 update includes all the software additions of the penultimate version of Android, plus such additions to TouchWiz as Samsung has deemed necessary. Specifically that means Galaxy Gear support, new drivers for the GPU, a basic Apps2SD implementation, new voice commands, various visual tweaks to match the Galaxy S4 and Note 3, and a driving mode, among many other things. To check for the update use your Settings menu, tap More, then About Device, the Software Update.
Like most manufacturers, Samsung tends to send their software updates to different regions and carriers in batches. Given the popularity of the Galaxy S III, it may take weeks or even months to distribute software to all the various markets and carriers where the phone is being actively used. We'll be updating this post if builds are delivered anywhere else in the next few days.