I bought a D40 new from Westpoint Nissan in Brisbane. They were absolutely hopeless to deal ith during the sales process, and then on it's first service it was returned to me with a dent in the bonnet, probably from a spanner or something like that. When I told them about it and asked for them to fix it when i picked the car up that afternoon, they basically accused me of lying.
I bought my D22 a few months back from Zupps at Beaudesert, only because they gave me the best price. They were friendly and everything went relatively well. As I live in the city, I didn't have any intention of using them for servicing, purely because it's about 1.5hrs drive.... so I use Metro Nissan in Windsor. They have been quite good, they did a good job in dealing with my diff fiasco where the car was off the road for 6 weeks out of it's 3 months life due to a failed rear LSD.
As for Nissan Australia, their customer service is basically non-existent. I have sent several letters to their "customer care" department, with no reply. Which reminds me, it's time for another follow up letter.....