Block Island is an overcrowded spoiled island. It's charm has led to its fall, in my opinion.
Aside from the madness of traffic and crowds who arrive by ferry and spread across the island on bikes, scooters, taxis and feet.. there are the hundreds and hundreds of boaters who descend on the place from NY, CT. RI and MA.
It's a fav spot for sport fisherman and the marinas raft boats many deep. Disgusting in my opinion.
The dinghy dock is mega crowded and getting a tie up or onto you dink and out again can take serious time. If that's your idea of fun... go for it.
The Oars right on the dock is where sailors go and get drunk and obnoxious along with local youths.
As Bill says you have the option of the Oldport launch if you have the time to spend going from boat to boat as they pick up and drop off customers. This can take up to an hour to finally get to your boat or from your boat to the dock.
Having said all the above, off season BI is really delightful. No crowds, and you can enjoy the island as it was 20 or 30 years ago before it was "discovered". I think the off season population is less than 1,000 and in season it may be 20,000 or more.
When the wind pipes up or squalls come through the anchorage is a madhouse of dragging unoccupied boats. The evenings are filled with the sound of generators and outboards and the smell of grilled food.
It's a fun sail, but my wife hates it and we won't go there in season. You need to experience it though. Don't believe me.. find out for yourself.