Ease of use isn't a strong area for the Sony KD-84X9005. The most disappointing thing is the appearance on the TV of the same fussy and frustrating double-axis main menus sported by Sony's other current televisions.

These menus are delivered at the same resolution as they are on Sony's non-4K models too, meaning that their text looks blocky and grubby - hardly the front end experience such a cutting edge, resolution-obsessed TV should be presenting.

Things are at least a bit better with Sony's SEN menus. These are much prettier and more logically organised than those of previous Sony TV online systems, making browsing a much more tempting prospect.

Sony KD-84X9005 review

The addition of a Favourites section where you can shortcut your favourite apps is extremely welcome. And the implementation of Twitter as a ticker underneath a reduced version of the TV picture is inspired.

However, we feel a bit sniffy about Sony giving its own Music and Video Unlimited services the lion's share of the SEN menu space, while the likes of Netflix and Lovefilm are relegated to a general 'apps' menu. And there's also scope for Sony providing more direct links to more content by using smaller icons or a higher resolution menu system.

Sound

Sony seems to have put almost as much effort into the Sony KD-84X9005's sound as it has its pictures. And the results are, for the most part, terrific.

Bass levels, for instance, are miles deeper, richer and more effective than those of any ordinary TV - which is, of course, particularly handy when you're rollicking through a Blu-ray action scene.

Even better, the healthy dollops of bass the Sony KD-84X9005 can produce don't overwhelm the mid-range, thanks to the open flavour, clarity and raw power of this most important section of the audio range.

Sony KD-84X9005 review

Even trebles are well served, adding bags of life and detail to the mix without ever sounding harsh.

Our only concern with the Sony KD-84X9005's sound is that voices can sound dislocated from the action - as if they're appearing from the left or right edge of the screen - unless you sit in exactly the right place.

This problem is alleviated a little by the way you can adjust the angle of the speakers, but a more dispersive approach to the mid-range would still fit better with normal family viewing situations.

Sony KD-84X9005 review

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There's also a philosophical argument here. As in, should Sony have bothered putting together such a potent audio system for the Sony KD-84X9005 when it will very likely be partnered with a high-end separates audio system?

But then Sony decided early on in the Sony KD-84X9005's development cycle that it wanted to make it very obviously a TV rather than a 'mere' screen. And if you're making a TV, it needs sound.

And if you're going to add sound to an 84-inch 4K/Ultra High Definition TV, it might as well be bloody good.

Value

It's a sad but unavoidable fact that the vast majority of the world's population will not be able to even dream of affording the Sony KD-84X9005.

It also seems likely from what we're hearing that the Sony KD-84X9005 will be quite a bit more expensive than upcoming 84-inch 4K TVs from LG and Toshiba.

And it's even more expensive in the UK than Sony's own 4K/Ultra High Definition projector, the VW1000ES.

Sony KD-84X9005 review

On the other hand, the Sony KD-84X9005 is easily the most exciting, adorable and AV life-changing TV we've seen. And we are confident that Sony's 4K X-Reality Pro processing contributes a substantial boost to the Sony KD-84X9005's native and upscaled 4K performances over and above the quality that the other upcoming 84-inch 4K TVs will likely be able to deliver.

Some will question the wisdom of investing £25k/US$25k in a technology - 4K/Ultra High Definition - that's not even guaranteed to become a widespread commercial reality.

But don't forget that the TV does also upscale HD extremely ably. And anyway, if you can afford such an expensive TV, the chances are that you're wealthy enough not to need to spend too long justifying the outlay.