I have one, and I've only been toying around with it, but I've been fairly impressed. The hardware is very nice - polished, while still keeping everything acces

I have one, and I've only been toying around with it, but I've been fairly impressed. The hardware is very nice - polished, while still keeping everything accessible. The software is pretty decent also. The documentation leaves something to be desired. That said I don't see it as completely overlapping with the Pi. The ESP32 in the M5Stack is a much less powerful system in terms of performance, memory, storage, etc. It's not running Linux, so your code is much closer to the metal. That can be both good and bad depending on what your goal is: you have much more control over the hardware but it limits your choice of programing languages and what existing software you can depend on.