We just played this in my campaign. I dropped it into an adventure already going. It was a great side trip. The module worked well. The adventurers like it and found the sea hag quite a difficult case.
If I run it again, I would redraw it with a little garden and with one more complex with bugbears. Maybe I missed something in the design when I DM'ed it, but the garden was not very interesting to my adventurers. I would skip the undead treant as they don't fit in the rooms well. It was hard to explain how the tree would attack from the wall. Did not need 'em. Just a few changes and it would be perfect for my style.
Over all we liked it and it played well. The town was a trip with the little dog leading the adventurers to the garden. It is a good side trip and is best slipped in as the adventurers are traveling. Buy and use it!