Fewer tourists but everything is still open. More wind, but without the serious storms we get in October. Temps are cooler and humidity is lower than in July/August so being out on the water is more pleasant. Because there are fewer boaters from away, the anchorages seldom fill up or even get mildly crowded. October can be nice too, but you will want a heater for evenings and there are often some pretty significant gales.
We do most of our longer distance trips in the Fall for the reasons mentioned above