We went Admiral floor when we stayed at the NBC and we thought it was worth it! The breakfast is very busy in the hotel so having room service is lovely! You have a dedicated check-in for Admiral Floor guests and this is great if you arrive along with a big crowd as we were the only ones using it when we arrived and there was quite a big Q for regular check-in. Our room was quite a long trek so make sure you ask for a room closer to reception if you don't fancy a long walk at the end of the day (on the plus side we were right at the end and it was extremely quiet - noone had to pass our room).
Enjoy your stay!