The Sony 'Concept for Android' is a stripped-back beta version of its usual Android UI. It's being tested on 500 lucky Z3 owners in Sweden, but as you'd expect from the internet, screenshots (and a full copy of the software) have leaked out.
Without a Sony phone to hand, I can't test the software myself (believe me, I tried); but I can gawk at the screenshots. It looks pleasantly close to the version of Android 5.1 Lollipop on which it's based -- and that's a very, very good thing.
Handset manufacturers tend to gum up their Android skins with garish designs that ruin Android's Material Design, and excess apps that you can't install. Sony's Concept retains most of the design of Lollipop, and only adds a few apps: Album, Music, What's New, and Xperia Lounge. That's orders of magnitude better than the old Sony software:
There's a loooooot of crap on [the Z3v], and by crap I mean pre-installed shitty apps I don't need or want. Let's take a look: Amazon Kindle, Amazon Music, Amazon App Store, AR Effect, Audible, Background Defocus, Caller Name ID, Verizon Cloud, Lifelog, Messages+, Movie Creator, My Verizon Mobile, NFL Mobile, Smart Connect, Softcard, Sony Select, Update Center, Verizon Voicemail, Verizon Navigator, VZ Protect, What's New, Xperia Lounge and more.
It's kinda sad that I'm excited for software that's unchanged from the original designer, but it's also true: I'm sick and tired of rooting Android devices, or even just messing with them for hours to get a stock feel.
If Sony ships future Xperia phones running this version of its software, it will join a short and exclusive list of Android manufacturers who haven't wrecked their hardware with bloat. Meaning there might be more than one Android phone I'd seriously consider using out of the box. And that is exciting.
If you've got a Sony Xperia Z3 and you want to test the ROM for yourself, XperiaFirmware has all the files and instructions you need.
Screenshots from Swedroid