The Sony Xperia Z3 comes with the latest Android 4.4.4 KitKat out of box with the latest Sony improvements to its custom Xperia overlay.
Here's a demo of what the Xperia Z3 can do:
The lockscreen is the usual affair - it supports widgets (one per pane), alongside a camera shortcut at the bottom. There are a few available default widgets, but you can always get more from the Play Store. Also third party apps oftentimes come with their own set of extra widgets.
Naturally, you can protect your lockscreen by Face, Pattern, PIN or Password unlock, in ascending order of security. With the Xperia Z3, Sony has also included tap to wake, which lets you activate the screen with a quick double-tap.
The Xperia Z3 lets you add or remove homescreen panes (you start with five) and set any of them as default. You can't have more than seven panes at any given time though, nor can you change the order they're in.
Adding stuff on the homescreen is easy as customizing it. You can set various live and static wallpapers, add widgets and shortcut, or change the UI theme.
The notification area loses the quick toggles, which have been moved into their own separate tab. You can gain quick access to the Quick Settings tab with a two-finger swipe from the top. The toggles are customizable and you can choose between 20+ different toggles and have up to 12 of them visible on their dedicated pane.
The app drawer is laid out across multiple pages and you can sort the apps manually, alphabetically, by the most used or most recently installed. The menu with these settings is accessible via a swipe from the left edge of the screen and you can also search and even uninstall apps from there.
The Xperia Z3 uses the stock Android task manager that lets you switch between recently opened apps, as well as terminate them with a side-swipe.
The so-called "small apps" are also available in the Xperia Z3 and are accessible via the task manager. They are similar to Samsung's Mini Apps, and pop up tiny widget-like applications on your homescreen, which you can move around and use without having to open the full-fledged app. So far, there's a default set of nine: Active Clip, Chrome Bookmarks, Browser, Calculator, Calendar, Gmail, Timer, Notes, and Touch Lock. You can launch only one instance of a Small App, but you can open multiple Small Apps simultaneously.
You can download more Small Apps off the Play Store or use the option to turn your favorite widgets into Small Apps. Just hit the Plus key at the top of the list and choose a widget.
Naturally, you can access Google Now by swiping from the bottom of the UI. There's another shortcut right next to the Google Now launch key called What's new. This app has a very slick UI and will show you the hottest apps and multimedia today. It isn't limited to just the Google Play Store, and will display content from Sony's PlayStation store too.
Finally, Google Now integrates with your Google account and can access your daily routine, internet searches, email, etc. and give you information relevant to your interests and daily needs.