I've had this for a couple of months now, and I'm quite impressed with it. Stumbled upon it from a Facebook ad, last summer, and its design was the first thing that caught my eye. My previous phone was an Essential Phone, which is quite similar to Sony's design; sadly they are no more. It was also a main thing why I decided to switch from it, other was depleting battery. It also reminds me of an iPhone 5, whose design I adored, although I never got into it, due it being an Apple device.
Camera is excellent; the difference is huge, comparing to my previous device, Sony allows bootloader unlock and root (which can void your warranty though), battery is enough to last two, three days without charging, which is significant improvement.
Aspect ratio of the screen is a bit strange at start, but more than welcomed, if you get an opportunity to watch movies with it. I tested it briefly with 4K HDR material and results were impressive.
There haven't been significant heat buildup so far; though I installed the latest updates into it immediately when I got my hands on it. At least it's not dying on you if it gets exposed to a cold weather, like my previous phone.. :)
MicroSD card slot is also an absolute bonus, and for me, a necessity. So is headphone jack, though I rather use a separate Bluetooth transmitter to connect my headphones to the phone, so I don't have to keep the phone in the pants pocket.
Speakers are also great, and the audio application handles big (in my case, +35 000 songs) music libraries without hiccups.
It might be a niche product, for niche people, but those who get it, will love it.