There is definitely a novelty about the AO. There's virtually no build up to it and the next largest ATP events are almost two months after it, yet, it holds huge implications for the rest of the year.
Also, living in the U.S., it's definitely fun to be watching live, epic matches in the middle of the night (even on school nights)! I usually fall asleep with the TV on so I can get a few glimpses of the night matches. I always stay up to watch the final, though, and watch it through to its conclusion. I love this sport!