Xperia ZU.

Sony enters the big leagues with a 6.44-inch screen and the latest Snapdragon 800 CPU

Sony hasn't always found itself ahead of the technological curve when it comes to smartphone internals. Often it's lagged a generation of so behind the competition, giving the likes of HTC and Samsung the first shot at releasing phones running the latest mobile chips. Yet here we sit with one of the very first Qualcomm Snapdragon 800 devices, and above its ginormous screen sits a Sony logo.

Say hello to the Xperia Z Ultra.

The Ultra, as we'll call it, is also a first in terms of Sony's product portfolio. It's the first time the Japanese manufacturer has attempted a phone/tablet hybrid device, and the Ultra's 6.44-inch screen pushes it well beyond the realms of mainstream smartphones. With 5-inch devices now the norm - Sony itself released the Xperia Z and ZL internationally back in February - big screen phones are getting bigger. It's hoped that the Xperia Z Ultra's extremely svelte body will offset some concerns over its usability, however, and at 6.5mm it's definitely one of the thinnest phones out there. Like the Xperia Z, it's sporting a glass-backed design, which gives its chassis a classy, uncluttered appearance.

That said, this isn't what we'd call a mainstream handset, and using the Ultra one handed can be tricky. Aside from its sheer size, this is partly due to the design heritage it shares with the original Xperia Z - that phone was blocky and squarish, and it's ergonomics suffered as a result. The Ultra's thinner chassis goes some way towards compensating for this, as do its new, curvier sides. But for most users, this isn't going to be a device you can easily palm and operate at the same time. In addition, one notable tradeoff that's made in the name of thinness is the rear camera sensor size, which has been bumped down to 8MP, compared to the original Xperia Z's thirteen. It's also disappointing to see LED flash being omitted on a high end device. Sony has however managed to cram in a hefty 3,000mAh battery (non-removable, of course.)

Xperia Z Ultra. Xperia Z Ultra.

The Xperia Z Ultra's external heft is matched with suitably beefy internal hardware. As we mentioned, it's the first device we've used with Qualcomm's new Snapdragon 800 SoC, which incorporates a quad core 2.2GHz Krait 400 CPU and a new Adreno 330 GPU. What that means is it's fast - really, really fast, in fact. The device flies through regular smartphone tasks, and from what we've seen it'll destroy most current chips in synthetic benchmarks too. We'll need to spend more time with a final retail device to be sure, but for the moment the Xperia Z Ultra shows signs of being one of the speediest smartphones around.

Sony's "Triluminos" display also impresses.  Gone are the days of Sony phone screens offering lackluster colors and poor viewing angles - the company's latest 1080p panel offers rich blacks, wide viewing angles and vivid colors. The Ultra's 6.44-inch panel is right up there with the latest SuperLCD3 and SuperAMOLED offerings.

The device is also waterproof and dust-resistant, and is rated IP55/IP58, an improvement upon the original Xperia Z's IP55/IP57 rating. As such, you'll still have to deal with the plastic flaps which protect various ports, though the 3.5mm headphone jack is exposed and fully waterproof this time around. In addition, an official magnetic charging dock will be available to make your daily charge a little easier.  Unlike the Samsung Galaxy Note series, the Ultra doesn't include is own stylus. However Sony is advertising the device as having drawing support for pencils, capacitive styluses and metal pens with a diameter of more than 1mm. It's not quite Wacom (the technology used by Samsung's Note) but it works well enough.

Xperia Z Ultra.

On the software side we're dealing with Android 4.2.2 Jelly Bean, lightly skinned with Sony's Xperia UI. The software interface hasn't changed too much from earlier incarnations, but it's noticeably smoother than before, and it's closeness to vanilla Android (and use of onscreen buttons) will please OS purists. Atop the latest version of Jelly Bean you get the usual Sony multimedia apps - Walkman for music, PlayStation Mobile, Music Unlimited and Video Unlimited - and new on the Ultra is the preloaded Sony Reader app. Naturally, if you're living in the Sony ecosystem you'll be right at home here.

The Xperia Z Ultra is due for release globally sometime in Q3, and our brief time with the device has left us impressed. This isn't a mainstream phone, but just like the Galaxy Note line it's not really trying to be. Sony's aiming for a heavy hitter with the Xperia Z Ultra, a device targeted at the growing audience of buyers who want a sizeable mobile device - something larger than a phone yet smaller than a tablet. And for the moment, Sony's 6.44-incher is the best big phone we've seen.