My Roomba 770 has finally started die after 5 years of hard work (5 days scheduled vacuum per week), Myer has the best price by far on the 880 right now. iRobot sells this for $699 USD direct.
Is also available on their eBay page: http://www.ebay.com.au/itm//231843297236
Wasn't available for me in store but their eBay does free delivery.