[Xperia Z5 Q&A, Help & Troubleshooting] MickieH:
I thought I'd tell you all what I've noticed after using my Z5 for a while now.

I find the UI to be quite laggy at times, especially after pressing the clear all button. It seems to stay on the screen with the small apps launcher bar at the bottom for quite a while, before it returns to the main screen. Launching apps for the first time takes longer than I expected, but they do launch fast the second time, unless you've cleared it from memory by swiping it away on the recents screen. There are videos on YouTube comparing the Z5 to the new iPhone 6s, and I was pretty shocked to see how bad the Z5 performs against the A9 processor of the 6S.

It does get quite hot during normal use, or when syncing data, like my Google Photos album (but there are over 20,000 pictures backed up.) Definitely hotter, faster, than my Z3. A fridge is handy at times like that to keep it cool. Don't want to fry the battery. It also get's hot on first boot too, after resetting, and it will be the same after clean flashing new roms (eventually). I'd only taken a handful of photos today, when the camera overheated the phone, and I got the 'camera unavailable' message. Strangely, they were only normal, auto mode photos, when my previous phones only ever really did that when I was using other modes, like the AR effect, or whatever.

The battery does drain pretty quickly once you start using the phone, yes. While it's idle, it's not too bad as long as you pick the right power saving features, like no WiFi with screen off, and no WiFi scanning being always available, but start messing around and you can see the percentage dropping. Nowhere near as good as my Z3, which I've kept, thankfully. Turning on 'Extended usage' in the Stamina mode menu hasn't seemed to have had any beneficial effect either. I don't know what kind of governor that uses, or what CPU speed it is restricting too, but I wish I had root so I could use my own governor. Just have to wait I guess.

I found this bug to be quite unexpected too. If you look in the contacts app, if you have a contact picture with a white, or light coloured background, try reading the writing, the contact name, or finding the buttons in the top right corner. The contacts app on the Z3 seems to darken the bottom and top edges of the images so these are readable, but the Z5's current firmware doesn't.

There's probably other things, but I tend to play around on my Z3 more to save the battery on the Z5, so I haven't found anything else yet. If I didn't have my Z3 still, the 5 more than likely wouldn't even last me a day, and I don't play games, or watch loads of video or anything. My Z3 easily lasts me virtually the whole two days. I'm a caller/texter mainly, and often plenty of photos, but I do have Wifi on unless the screen is off because I use WhatsApp, and Facebook sometimes too.

Turn your WiFi and mobile data off and the phone behaves itself very well, Shame every time I turn the screen on, I seem to need internet, so hey ho there.

Considering this is 5.1.1, you would have thought it would have been nice, clean, and smooth, but sadly, no. I'm hoping that the smoothness of the firmware will be sorted out once the updates start rolling, but I'm not going to hold my breath on battery life, and I've pretty much resigned myself to charging it at least every night. I beg Marshmallow has some better battery management. Maybe the new Doze feature will do something? Well, I wanted faster, more power, more memory, and don't forget awesome looks (mine is the Gold version) so I guess I can't have my cake and eat it.

I notice that they've now added the Z5's model number to the PTCRB website, but no firmwares are listed yet.

I hope the updates comes soon, and that they don't leave the final Z5 Lollipop as bad as this release.

P.S.

I do love the phone, I've always had Sony for a long time now, but it could have been better.