I like the feature where you can take the battery out and use it on mains.
I don't know if they've resolved it with the M3s but the M1s were a bit hit and miss with this.
Mine (and lots of others) would constantly reboot itself if the battery wasn't in it but lots of other people had no issues at all doing exactly the same thing.
I did wonder after I sold it if this was because the voltage might have been spiking and if a regulated supply might have cured it, but I'll never know as I can't test it now