I'm going. I went for the first time last year. Advice: take something wind proof, it gets mighty cold just sitting by the track, especially if the wind is blowing hard, which it will.
I camped last year, and it was 2 degrees C at night, with a frost. So take plenty of warm clothes.
Oh, and don't forget: period dress! About 80% of the people who go will be dressed in 50s and 60s clothing. I don't know of any good shops for selling that sort of stuff (if you do or find any, let me know please!).