Works great for joy-con charging. I'd rate it higher (5star) if it had 2 design changes.
1. If it were able the charge the NES style joy-con controllers.
2. If ir had another USB port on it to charge Pro Controllers as it takes up the only charge port on the Switch Dock. So to charge your Pro Controllers, you need to unplug this from your Dock, and plug in the Pro Controller USB-C cable.