Grumpy's is a cute little place tucked out of the way right on Southwest Harbor, next to the Marine store. Nothing fancy. We found it the next day after we arrived in Southwest Harbor. Saw it listed in our condo's guest book and just thought we would give it a try.
Mind you we vacationed the early part of June so there were no crowds, which we prefer so our review is based on pre-season experience. Depending on where you sit, you can have a nice view of the harbor. Also have seating outside. Breakfast for two was about $20-25. If you like French Toast, there's was delicious. Had that both times we went for breakfast. My husband had an egg dish with hash and he said the hash was very tasty (I don't like hash but I tasted it and it was good). We didn't feel rushed and the owners were very nice. Both times we went there were a number of locals so that gave us a sense that they have good food.
We would suggest giving it a try.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.