Designed to be a celebration of Australian history and the unity of the Australian people, it was never intended to be controversial, but some have criticised it for being culturally insensitive.
Today, Australia is a multicultural country, but in recent years there has been a lot of objection to so called boat people 'invading' the country. The ad makes the point that we are all boat people really, except for the original inhabitants, and that who is an invader or not is just a matter of perspective. It is all done in a light hearted way.
Some in the aboriginal community have insinuated that Australia day represents the start of hundreds of years of oppression and that it is inappropriate to make fun of such tragic events.
Personally I don't see what all the fuss is all about. I think it is a good ad, but then again I am just a middle aged white guy that came on the boats myself (well actually it was a plane). It was never likely to offend me. At the end of the day it is just an ad trying to sell lamb and we shouldn't read too much in to it.