@ocken

Sure, tons of thins.. Your typical rechargable battery doesnt have any sort of power management, its a raw cell. Since the chemistry is not the same as non-rechargables they have a different nominal voltage. This means many/most rechargable batteries wont work in many devices. When they do work their voltage is so low they will drop out before getting anywhere near using full capaicty, which is an issue since they already have far less capacity than a Liion or alkaline.

So there is that, that you cant use them in many things, and when you can loose a big portion of capacity.

These batteries have built in regulators. So they keep their voltage at the nominal voltage for their whole life. This means you get to use most of its capacity, and Liion has much higher capacity than other rechargeable types so that gets you a long long way.

In terms of down side, only one I know of. Because of the battery regulation there are 2 consequences:

1) You usually can no longer use a wall charger, you have to use USB-c

2) Battery level indicators wont work anymore as it shows a full charge right until they die.

There is also the advantage that you no longer need to buy or carry a battery charger.. use these in all your devices and you always have a usb cable on hand.

@jesse