5 or more years ago the Nats was quite rowdy, the last few years it's tamed down so much especially with the increasing numbers of security.
The Summernats is no different to a weekend nite club in any major city, if you go looking for trouble you will find it, if you arent looking for trouble you won't even see any.
Also about it being an event for the v8 bogans, I think the "v8 bogans" vs "jap ricers" would be nearly identical in numbers if you take into considering all cars in the carpark and cars cruising braddon etc - not just cars located inside the arena. It's quickly changing from a pure v8 muscle car event (majority are 30-50yo's) to a younger tuners event.
I'll certainly be there again this year