I'm also in Canberra and I've had a different experience to Nemo. I signed up before it opened (got caught up in all the hype) and hubby and I go there around once a month and stock up mainly on toilet paper, paper towel, cat food, up 'n' gos and some of their meat. For us the saving on these items is worth the membership alone. I very rarely see woolies or coles get down to the same prices on cat food even when on sale. They also have my hubby's fave jeans, the Levi's 501's for about half the price of Just Jeans ($45 compared to $120). Again, that covers the cost of membership as he goes through a pair a year.
I think it's great. There's only the two of us and two cats and I still find value from my membership.