Yes it is definitely worth being there for a show at night, if it is something on you'd enjoy. So check what will be on in March-April, 2023. It is worth getting there early to soak up the atmosphere and enjoy the unique architecture whilst looking out of the big sails at the Harbour.
If there are no performances when you will be there, it would be worth going on a tour of the Opera House, as you see more of behind the scenes.
I enjoy riding the ferries and having lunch at the destination (Manly, Watson's Bay)