We ate at Il Buco, which has (I think) a Michelin star. It was attractive and expensive, but as a frequent diner in NYC, I didn't think it was really worth the money - in a country that is filled with magnificent, low-priced dining. One issue is that Sorrento, while attractive, is a very touristy city, with a large number of budget-driven sun-seekers from rainy climates in Northern Europe. That drives down how ambitious a restaurant can be, and remain in business. There's plenty of "satisfactory" food in Sorrento.
One of the best meals we had in the area was a modest weekend lunch in Sant Agata sui Dui Golfi, surrounded by small christening and confirmation parties, Da Mimi. It has a walled patio for good weather. And it's not far from the 1.5 hour, all downhill, 99% paved walkway back to Sorrento. Left, out of the restaurant, then a bit of searching. SITA bus to Sant Agata leaves opposite (across the street from) the Circumvesuviana station, to your right facing the station.