BBAU is generally boring and not worth the time spent watching it, and if you're into drama and fighting, it's definitely going to be a letdown. I would recommend watching them in a row if you do plan on seeing all of them, in part because they often spoil the results of past seasons by having ex-HMs on as guests during the live shows.
BB1 is good but most people would probably (unfairly) write it off as dull. BB2 is an unholy abomination and makes BB4UK seem like edge-of-your seat viewing. BB3 is the only really outstanding season; there's plenty of drama, a great cast, the best launch night twist of any country, and the return of Anouska <3. After that the producers decided to turn the show into a really low-brow douchefest and just put in stereotypical young Ken and Barbies who would be willing to shower naked... yet they don't show you the nudity on the highlight shows
It's like this from BB4-BB7 and they're all god awful seasons except for BB5 which was saved by having an amazing cast regardless of the fact that they were marketed as being "single and sexy" or some ridiculous marketing slogan
BB8 is good because they copied BBUK and the house was better, cast was much more diverse, and there was drama and nearly physical fighting <3 Unfortunately they were also inundated with constant celebrity guests.
But be warned, the Australian public are the worst voters in the world, so just go into this knowing that they are going to **** the evictions up every week.