Sony's XZ Premium flagship has just about everything you could ask for from a top-end phone. A 4K display, insanely powerful processor and a unique super-slow motion camera all make this handset great.

And yet I'm not completely smitten.

Beyond the headline-grabbing spec list, the XZ Premium needs more refinement to justify a Galaxy S8-bothering price of £649 in the UK. In the US, the XZ Premium will cost $800 when it goes on sale June 19 with Amazon and Best Buy. While Sony has said the phone will be available in Australia, it's yet to announce pricing. For reference though, that UK price converts to about AU$1,090.

With a list of specs to trouble the biggest smartphone players, Sony had the recipe for a truly superb flagship phone here. It suffers from an overall lack of finesse, however -- most notably in the same-old-same-old design, which is in dire need of an update. If you care about looks, this XZ Premium simply falls short of its rivals. And its stand-out feature, a super-slow-motion mode that Sony does better than any other phone rival, while intriguing, isn't enough to completely smooth over the phone's other camera and design flaws.

There's no question that the XZ Premium is a great phone overall, but competition at this price is fierce. The Samsung Galaxy S8, which costs the same, offers a more refined experience and won't leave you feeling like you've spent all your money on last year's hardware. (Scroll to the end for more comparisons with top phones.)

Shiny, but still needs a polish

The Xperia XZ Premium's mix of glass and metal fits the "flagship" bill nicely and the shiny chrome back stands out from the crowd (plus, it doubles as a handy mirror). But its overall look is tired. The angular, monolithic design has barely changed in the last few generations so we're still left with a thick bezel around the screen, making it unnecessarily chunky to hold.

With Samsung continuing to refine the sleek, curving edges of its Galaxy S8, it's really time for Sony to retire the XZ Premium's overused aesthetic and try something more up-to-date.

It's waterproof, which is good, but it still uses a rubberised flap to cover the SIM and microSD slot, which is annoying. You'll have to make extra sure it's pushed right in before you go near the pool.

Tired design aside, this phone does have plenty to shout about. The 4K display (3,840x2,160-pixel) is pin-sharp, extremely bright and has colours vivid enough to melt out your corneas. The Snapdragon 835 octa-core processor is extremely powerful, handling demanding mobile gaming and photo editing without hesitation. There's NFC and a side-mounted fingerprint scanner for Android Pay contactless payments too (frustratingly, this is turned off for the US), and it comes with a decent 64GB of storage as standard.

Life is fun in slow motion

A new addition -- and the phone's best, most unique trick -- is the slow-motion video function. There's slo-mo and then there's slo-mo. Sony's phone turns it from a feature common to all phones into something really special. While the iPhone 7 ($799.45 at Amazon Marketplace) shoots at 240 frames per second, the XZ Premium tops that with 960 fps. Even mundane things like a common London pigeon taking flight look fascinating when you watch them back at a super-slow pace.

I've had a lot of fun playing with the function, but that too needs some work. You capture slow motion video by pressing record to start recording at normal speed, then pressing again when you want to capture a quick burst (roughly about a second in real time) of slow motion. You can only take a short burst of super-slow-motion, and it's usually trial-and-error in getting the timing right.