Sony's Xperia Z5 Premium is clearly an experiment with the top-end specs we'd love to see every phone include one day.
The 4K display really does deserve a round of applause – if you'd asked me 12 months ago I wouldn't have said Sony would be the first to break the 4K barrier.
But there are still some big issues with the Xperia Z5 Premium, which mean it's not the best phone money can buy right now.
The display technology is a step forward for the mobile phone industry. The Xperia Z5 Premium's screen looks gorgeous, and it's something I didn't think we'd see for at least another year. Sony has managed to cheat a little by not making it an always 4K display, but if it saves on battery and offers a high-res picture I don't really see it being a problem.
It might not look all that different to the 2K displays we've seen on a few flagship phones, but those who love to be first with the new tech will be delighted that Sony has jumped the 4K barrier and planted its flag.
The fingerprint scanner on the Xperia Z5 Premium is excellent, and I can't think of another company that has got its security tech right so quickly; even Samsung and Apple had to have a few tries before they got it right.
PS4 Remote Play and waterproof designs aren't a new thing for the Xperia brand, but we've never seen a phone this big include them.
The ability to enjoy your PlayStation 4 games on a 4K display while in a different room in your house is a great feature, and for gamers this alone is a good enough reason to buy a Sony phone.
Sony has claimed this is the best smartphone camera setup in the world. I don't think that's quite true, and there are some big issues with the camera, but it's a big improvement on previous Xperia shooters, and it's great to see Sony break new ground with this tech too.
The design of the Sony Xperia Z5 Premium is pretty lacklustre. There's nothing inspired, like some of the flourishes on the Xperia Z5 – I don't understand why Sony didn't decide to frost the glass on the back, as on the main flagship.
The plastic edges especially feel cheap, and a step backwards from the design of the Xperia Z5. The fact that this phone weighs so much more, and is thicker, only adds to the disappointment.
Sony's UI isn't anything impressive either. There's no step towards improving it over the offering on the Xperia Z3+, and if anything it feels like there's even more bloatware on this phone.
Heat-up issues continue to plague the Xperia Z family. The problem is nowhere near as bad on the Xperia Z5 Premium as on the Xperia Z3+, but no one wants their phone to heat up alarmingly while they're playing a game or just watching a video.
Battery life on the Xperia Z5 Premium just isn't good enough either. The cell isn't that much bigger than the one in the regular-sized flagship, which is a problem given the 4K display it has to power.
A long-lasting battery is one of the main features people look for in a phone, and Sony hasn't managed to make serious progress in this area before ploughing ahead with cutting-edge screen technology that we don't particularly need right now.
There's no denying that Sony was chasing headlines with the Xperia Z5 Premium. We should all applaud Sony for what is has achieved in putting a 4K display in a smartphone, but feels like this hasn't been done with the right intentions.
Battery issues were inevitable, and I'd really hoped that Sony had a plan to improve the battery life in the Xperia Z5 Premium. Instead, Sony has just hoped its battery would be sufficient and run with it.
This suggests that the Xperia Z5 Premium is more of an experiment than an attempt at making the best phone on the market.
The general specs of the Xperia Z5 Premium do impress, though. If you can live with that below-average battery life, and don't mind spending a bit more on the fast-charging adapter, you'll have a fantastic experience with this phone.
Sony has proved that 4K in a phone is possible, and I look forward to the next version – we'll hopefully be able to appreciate that display even more when some of the other issues have been ironed out.
It might not be as stylish a handset as the Xperia Z5, or as easy to hold as the Xperia Z5 Compact, but the Xperia Z5 Premium is the go-to phone for enthusiasts who want the next big thing.
It's just a shame that it's not a more rounded package that everyone else can get excited about.
- Read our review of the Sony Xperia Z5
First reviewed November 2015