it's pretty $#!T that we have classes on O-week, that does not happen in USYD or UNSW. But yea, the lectures are running on O-week, not many tutes is going to be on, the only stuffs I know on the first week is ACST200 tute (B***dy lecturer gave us holiday tute questions!) and COMP225 pracs. I don't think First-year students have their tutes in first week except ACST151.
For O-week this year it's four days (more than 3 days last year) and in the central courtyard, which is not as interesting as last year. Last year we had O-weeks by the huge lake and whoa we had bumping cars and giant slides which turned it to something like a theme park. I doubt that is happening in this year's O-week (central courtyard is sooooo~ small!!!). But the O-week in this uni is mainly for promoting university societies, unlike other uni where they hold "surviving uni" and lectures like that as well.