There appears to be some confusion (with some posts here) over private hospital insurance and extras.
The Medicare Levy (ML) and Medicare Levy Surchage (MLS) are differrent beasts. This post refers to the MLS.
The gov will hit those earning over 50k (single) and 100K (combined) with an extra 1% of taxable income if you do not have private HOSPITAL cover. Fringe benefits and dependents further impact whether or not you are liable for the MLS.
Private hospital cover does not generally cover extras such as optical, physio, chiro, dental etc. It simply means you become (if you elect this at the time) a PRIVATE patient in the public hospital system. This is what the gov wants...
The gov does not care whether you do/don't have extras cover. This is not taken into account in the assessment.
Whether you choose to have both (private hospital cover AND extras) is up to your situation. You could choose, for example, to take out BASIC hospital and self-insure for extras (as we do).
In considering what to do you should take into account your age, financial situation, general health, family etc. Further, you should be aware of the Lifetime health cover rules - as this will likely bite your bottom later in life if you don't plan.
In our case we always elect to be a public patient (even though we have private hosp cover). If you do not elect this (you'll be asked) you're likely to be hit with extras. It might seem ridiculous to have the cover and elect to go public but that's the system we've got. We had one child in the private and two in the public system. The private system cost us just over 2.5K (WITH private cover - and not the BASIC cover). The public system cost us about $20 for pharm each time. We also found the public system superior. The choice of Dr did not concern us. But that's us.
In the end, you should investigate all possible impacts and understand that you're needs/requirements might well change as your life changes.
Cheers,