Good, very valid point made above about checking everything out first.
I'm not familiar with the VOIP options available to you in OZ, but I would also look at the financial strength of the company. There is a lot of competition, some aggressive with the landline companies losing market share to the VOIP carriers. The service we had then derided the VOIP concept and quality, which a few years later they were forced to embrace. Today they are now marketing VOIP themselves with discounts and other offers to return to the fold. ( Once gouged, never back )
For our family it was a no contest decision: We now pay 1/10 of what we paid in the past for monthly service, which did not include dedicated FAX service on a separate line, conference calling, overseas charges, and e-mail phone messages. The sound quality is very good, but then again they are B&O phones.