You might want to check out the latest edition of the ACCC's
"Measuring Broadband Australia" report:
https://www.accc.gov.au/system/files...ary%202019.PDF
This gives some statistical information on how the major RSPs (including iPrimus) perform, but they don't go into issues such as value-for-money, customer support, resolution of issues with NBN, etc.
Hope this helps!