I have a feeling when I read all the comments on La Boa tours to Capri that much depends on your captain. Ours was probably the same one as the people who had the bad experience (Promised a lot, deliver little comment). Our captain spoke very little English and pronounced so badly we couldn't understand. No one on board could translate for us as most were from North America or elsewhere in Europe. I understood that this was an English tour!!! So we had no comments at all except, pointing at a few spot, like this is green grotto, this is white grotto, etc. No history of the Island, nothing else, really. He drove like a cowboy, and managed to get everyone at the back of the boat absolutely drenched on the way back. The brochure says that we would "cruise slowly back" so we could admire the coast. That is not our experience at all on this tour. Also, there were none of the promised drinks, no cake, nothing offered. Also, he must have "conveniently" forgot to stop for a swim as the next thing we knew, we were back at the marina with no stop for a swim along the way. And while there was a "toilette" on board, there was no way one could use it the way this capitano was driving. You'd have to take your life into your hands.
The Isle of Capri is worth seeing for sure, make sure you go up the tramway to the town of Capri proper. We then made our way via the local bus to the other side in Anacapri where we grabbed lunch. That was a little less crowded than the Capri side.
So our recommendation would be to get a tour of Capri but do not use La Boa to get there as the quality of service is inconsistent.