The Captain Lord Mansion is simply wonderful. I've stayed here quite a few times, and it has always been magic. Don't miss breakfast; it's delicious (I recommend a soft-boiled egg and sticky buns, though the menu changes with the days of the week) and a great way to mingle with other guests. The review is right, though, that it's just not the same if it's overcrowded and your party sits in the dining room instead of the kitchen- so get down there early!
Merchant is definitely the most extravagant room but also the most expensive, and all of the rooms are wonderful and have their own character. Champion, a large corner room, is a fabulous second choice.
The town of Kennebunkport is also very charming- check out Allisson's Tavern, and in the summer, don't miss The Clam Shack. And don't be afraid to go up to Maine in the winter. I've been up many times in the winter and really enjoy the quiet, romantic atmosphere. Plus it makes the Inn feel that much cozier. Just don't forget your coat and boots!