Interesting thread.
An update: ING are offering a special at the moment - variable rate of 4.63% for borrowings over $1 mill. There are limited restrictions - PPOR needs to be P&I, unconditional by 30 Sep.
Their servicing is quite conservative, so you'd need to have decent borrowing power (not amazing, but comfortable) to get up to those loan amounts with them.
Pretty great deal, especially given they have 2 year fixed rate options sub 4.7% too.