A good experience so far with the Inrico S100, my first PoC radio, especially on offer at £159.95 from Moonraker. Not being familiar with Android it took some getting used to, my last experience being with 4.2 if memory serves and I didn't take a shine to that. This has 8.1 (Oreo?) installed and it's free from bloat which is good, and as stated in Moonraker's description it is fully compatible with Zello.
I recommend the optional drop in charger and for me this was another reason to opt for the S100 instead of the T310 that I had first considered. It saves risking damage to the micro USB socket and rubber cover from repeated use and was a reasonable £23 at the time of purchase.

The good:
The Inrico S100 is chunky with a bit of heft, larger than I expected but a good size and fit. It seems well built and is classed as 'ruggedised' so I expect it could take some abuse.

It is LOUD! I believe it has a 2W audio amplifier and with the front firing speaker it doesn't need the volume turned up very high and it doesn't distort easily. Sound quality is really good for both TX and RX, although the Auto mic gain in Zello is too quiet but there is manual adjustment up to +20dB available. I have found +10 to +12dB works well and gives good clear TX audio.

Battery life, stated as 'More than 25 Hours standby time' is in reality MUCH more than 25 hours standby time. I haven't run it flat so far but at the time of writing it has been on with Zello running for almost 32 hours and has 35% battery remaining, with an estimated run time of almost 17 hours to go. That is with moderate use, mostly on receive where it will consume more power driving that loud audio, in and out of poor coverage areas including roaming, quite impressive in my opinion. YMMV of course.

Mobile signal performance has been very good. I didn't particularly want a PoC radio with an external antenna. This performs very well with it's internal antenna and I think it's a neater looking form factor. Wifi and Bluetooth performance have also been solid.

The 3 buttons along the top are non functional natively in Zello as I believe they are implemented for Inrico's own PTT applications, but they can be mapped to many different functions using Button Mapper. The only caveat is that the screen has to be on although there is probably a workaround for that, maybe involving rooting but I don't require that functionality. I have the orange SOS button on top configured as a secondary PTT in toggle mode, using Button Mapper.

The screen is good although small but it's a good compromise for this purpose and still larger than some of the alternatives.

The not so good:
Not much really...
The belt clip seems well made and secure, but it is VERY fiddly to fit. Captive screws would have helped here.
There is a startup melody with the manufacturer's splash screen that is REALLY LOUD and cannot be adjusted as it plays before Android gets going, so there's no easily accessible setting for it. I scoured the Googles and may well have missed something but I couldn't find how to silence or even quieten it down. Be prepared at startup and put a pillow over it unless you want to wake up the whole street.
On my unit, on odd occasions, the physical 'Back' button doesn't respond. I will be keeping an eye on this in case it becomes more than an occasional annoyance.

All in all, more pro's than con's and I'm very pleased with the Inrico S100 (with the optional drop in charger) and would highly recommend.