We did this two years ago. We stayed in Manly Beach and paid 300 bucks each to go out on a boat in the harbor for the fireworks. Quite spectacular. We went sight seeing the next morning and most things were open, and not crowded at all. Quite peaceful on 1 jan until later in the evening. Negative was that even though we were quite far from Sydney, we were still putting out 800/night for a mediocre 1bd suite.