The northern half of Australia is delightful in Winter - you don't really want to be there in Summer, as it is very hot and wet. I mean, plenty of people live there, but it's not especially pleasant, although one does get used to it.
The Southern part of Australia during Winter gets very cold at night, but can have beautiful days. By cold, we are not talking about Northern European cold, but you have to factor in that Australian houses are not built for cold weather. When the clouds come over and the wind blows it can get unpleasant, but not too bad.
I live on a high plateau, which gets down to -10C in Winter nights, but typically more like -5C. Depending on the weather - less rain, lower temperatures at night and fabulous days - more rain, higher temperatures at night but cold nasty days. But most of Australia is flat, so Winter is not too bad. People in Brisbane put on a light jumper.
