I love the idea of it, and I love how tiny it is. Will probably get one when money isn’t so tight.
But I was curious if the power button was accessible without lifting it. And it genuinely isn’t. Why does Apple like shoving important IO and buttons underneath the device. Good thing it’s light?
Oh and a funny thing was the staff had to loosen its mount on the table so you could turn it on.
I worked for Apple for 12 years, most of that as a liaison between front line hardware service locations and AppleCare engineering. Battery swelling is a normal Li-ion failure mode that is not related to leaving a device connected to its charger. If Apple had any evidence of that they would decline warranty service on swollen batteries based on the system report of how long it was connected to external power.
The Magic Mouse has the charging port on the bottom because the first gen model used AA batteries and not a built in rechargeable battery. When they moved to the rechargeable battery model, they didn’t want to redesign the whole thing so they put the port on the bottom. It’s bad enough design that Tim Cook uses a Logitech.
It’s not so much “constantly leaving it plugged in” as “constantly leaving it at a high state of charge” (near 100%) which naturally follows from the first.
In recent versions of iOS and macOS, Apple have added features to keep the battery at 80% charge as much as possible for this very reason - it massively extends battery life to not be at 100% all the time.