Depends on your circumstances. For example the Telstra free
calls in any hour you nominate may give a better total cost.

And you dont necessarily have to sign any 'contract'
to get a better total cost result either. For example
if you mostly recieve calls and make few, unison
may well end up being better, because there is no
effective access fee that you get with the isim and
they in fact effectively pay you $5.75 per month to
have their sim, with no upfront fee at all either.

I doubt it. Most likely its just optarse coming to
their senses and deciding that even at the isim
rates they are one hell of a ripoff that still produces
one hell of a cashflow for them with most customers
and it suits them to undercut vodafone, their main
competitor at that end of the marker.

subsidised handset?

It isnt a contact SIM

Yes and yes