Speaking as an American, I really prefer that books are written using the spelling and phrasing that is appropriate to the setting as well. Or appropriate to the situation. If the main character is Australian and has relocated to America, I'd rather see the Australian spelling because it's from the point of view of an Australian. I love reading books written with UK or Australian (or some other English-speaking country) phrasing and words. My husband probably doesn't like it as much, as I tend to then speak like that for a while.
One thing that really does throw me off, however, is the single quotes for speaking. I have greater difficulty looking past that. I much prefer double quotes.