No, charge every night would be way worse. My wife uses her Fitbit to track her sleep, and it does this very well (much better than her previous smartwatch). She also tracks how much she walks during the day. A smartwatch that has to be charged every day would be useless to her.

I have no idea about the UI that some people complain about, but my wife seems to have managed to get access quite a bit of functionality in her Fitbit, so I'd say it's good enough for its purpose.