The day trip is great. Views of the NE coast, a few hours in the town, and a very welcome swim on the way back.
It's slightly complicated getting to Acharavi - Car/Minibus/Donkey/Horse to Sidari with Noula/Sally/Hilary then get the bus outside The Three Little Pigs (which the Little Prince people used to own), and then the bus takes you to the harbour. The boat sails close enough to the shore each way for you to admire the expensive bling on the yachty population of Agios Stefanos NE sitting on their cramped pebble beach or the sweaty masses on the overpopulated sand of Dassia and all points south.
Be sure to take swimmies. After a couple of hours in Corfu Town in the summer you feel like chicken dippers in a microwave. The boat stops in cool blue water for you to jump off. It even waits for you to get back on.
Then back to Agios Stefanos NW - appreciating how nice it is.