I have sailed into and out of Northeast Harbor many times, but never during July and August when the harbor is chock full of boats with dinghies coming and going all over the place. On top of that there is often little or no wind in the inner harbor and you can easily find yourself without the ability to turn enough to miss a boat.
I don't like Northeast Harbor because it is so crowded during the season. I only go there early in the season or after about October 10th. I spent a nice night there this October as the only recreational boat with a person on board in the harbor. The mooring fee was even reasonable at $5