More like what makes the ACT so good is the fact that it's basically one single city full of middle to upper class public servants who aren't held back by the reactionary rural redneck and outer suburb bogans that those of us in the states have to deal with.
To address your points, while the laws in the ACT may only affect 350,000 people, it's better that there's at least one sane, if tiny, place in the country. Charter of rights? Every single other western nation has one. Do you think it's just a coincidence that Australia is the only country that doesn't have one and also has a government that censors entertainment on a scale much larger than just about any other Western democracy? If we had a federal charter of rights we probably would have been playing R18+ games since the beginning.
As for legalising gay marriage, the ACT does not have gay marriage, they have civil unions, just like Queensland, NSW, Victoria and Tasmania. Yeah, real crazy, out there stuff. If the climate wasn't so fucking miserable and it wasn't so tiny it'd be the best place to live in the country by far.
Good on the ACT for doing this, I say, though of all the pros and cons of the place, R18+ games is pretty insignificant, and will be completely insignificant by the time it's rolled out in the rest of the states next year.