I would probably book the concierge room. Let them know it is your honeymoon, and you might get some special treatment. You don't need the concierge as long as you are willing to do some legwork before your trip. You would need to call Disney Dining early to book your restaurant reservations. Otherwise, you'll have a great dining plan, but be eating at places that were not your first choice. The concierge can also book other special events (a specialty cruise, la Nouba, dinner shows), and recreation. You don't book concierge for the food, but it is nice to know that you will have it. Also, you get free beer and wine at night, so that might mean somehthing to you. It is going to cost a good bit more...maybe more than $100/night for Lodge Concierge, and $150/night for the Main Building Concierge. That being said, I always book concierge when it is available. The concierge is more about the level of service than anything else. For some, it is not worth it; for others it is a must each trip. The Grand Floidian has two locations for Concierge. The Royal Palm Concierge is in the main building, and it is the most expensive. It has a formal lounge and is located on the exclusive 3rd, 4th and 5th floors of the main building. Rooms here are very convenient to the restaurants and shops of the resort. Also, the monorail and bus top is directly connected to the main building. Most of the views are nice, but not outstanding. The best views and rooms are the Honeymoon Turret rooms, but expect to pay at least $700/night for those. The second level of concierge service is the Sugar Loaf Lodge Concierge. This used to be a "concierge lite" experience without the alcohol, but it now includes the same food and drink offerings as the main building. The lodge and lounge are exclusive, requiring a room key to access. The views here are of the pool or marina. You cannot see the MK or castle from these rooms. The lounge is located in the center lobby of the building, and it does lack in size for the number of rooms in the Lodge. Still, it isn't too crowded and you can usually find a table and chair to sit at. The lodge is very convenient to the main building, Gasparilla Grill & Games, The Grand Floridian Cafe, the quiet pool (really the main pool based on the number of people in each of the two pools), Narcoossee's and the Boat Dock.
For your honeymoon, go for it. Spend a little bit extra and feel really pampered. Just don't put yourself in debt to to the upgrade!