^^Canberra is really what you make of it. If you live on-campus, generally speaking, you should be fine - there's so much going on all the time that the ANU becomes like its own little village of sorts. In fact, I'd say the ANU is in a much better position than most other Australian Unis are in terms of being able to pull in extra-interesting social/co-curricular events, due to the fact that so many people live on-campus.
The only thing I would warn you is that Canberra's night life is averageish. After dark, it's usually the case that only clubs are open, and the clubs themselves aren't all that flash. That said, everything is also ridiculously close to campus (I can walk to the city center in five minutes from my room) and parties are usually more college-based, so it's all good.