Happy Moto Mod user here
I bought a Moto Z with JBL speaker mod and black herringbone styleshell in 2016. I bought a Motorola battery Mod just as the internal battery on the Moto Z was prematurely failing. Motorola offered a replacement Z2 Play, and it being a mid-range phone agreed to bundle in the Qi wireless mod. In any event they also fixed the Moto Z, so i have both phones and 3 styleshells and the JBL, battery and wireless charging mods. Both phones take SD cards while the Z2 Play takes 2 SIMs and an audio jack, so i use it in preference currently.
Day to day they're both great devices and the mods work as intended. When travelling with boarding passes or tickets on an app, a battery mod for long battery life is reassuring, while installing a second PAYG 3 SIM when overseas is a boon. I'd like more frequent security updates, and was put off by the premature battery problem, but Motorola more than made up for that. The form factor is still current, and IMO the mods have been value for money for early adopters. The phones all charge quickly too.
I moved to Motorola from OnePlus, with no regrets.