First priority. Make sure you retain Australian Tax Residency otherwise every single dollar you generate in Australia will be taxed at 32% as you will lose the tax-free threshold. This includes state pension.
Many non-O retirees are switching to DTV, but it's more worthwhile if you travel regularly out of the country. You can save a bucket load of cash if you've previously used an agent and the bonus is there's no need to visit an immigration office for five years - that's the biggest plus for me.