The Sony Xperia Z Ultra runs Android 4.2.2 Jelly Bean and should receive an Android 4.3 update, but as it stands it’s much the same from what we’ve seen on the Xperia Z1 and Xperia Z. Sony’s skinning of the UI is improving in terms of intuitiveness and stylish looks.
The most important thing is that the Sony's presence is not as overbearing as some approaches to using the Android OS and the widgets can of course always be removed.
Sony Xperia Z Ultra - Performance
For such a big phone, it’s great to see Sony give the Xperia Z Ultra the kind of power it really needs to excel. There’s a 2.2GHz Qualcomm Snapdragon 800 quad-core CPU, 2GB of RAM and an Adreno 330 GPU. It impresses in all departments. Navigating homescreens is a smooth and lag-free, web browsing is quick, streaming video is done with ease and it handles graphically demanding gaming with little issue.
The benchmarks back up the Z Ultra’s processing prowess. In the Peacekeeper browser benchmark it score an impressive 789 putting it just below the iPhone 5 (907) and the iPad 4th generation (951). Running the 3D Mark Ice Storm benchmarks, it scores a 16770 putting up there with the Samsung Galaxy S4 (17732). The Geekbench 3 multi-core registers 2523 well above the Galaxy S4 (2076).