Would advise you get the insurance.
We have been here for nearly a year now and just got around to organising the insurance in December. Through various mishaps it did not come into force until 25 Jan and there was a lie period of til 25 Feb in which they would only cover accidents. On 16 Feb our son was admitted to hospital for 5 nights and we got out yesterday after another 4 night stay. Needless to say the insurance company will not pay and so far we have spent $5000.
The reasons we had dragged our feet a bit on the insurance was that we were covered for out-patient care through our work and are all well etc so were shopping around (without much commitment or enthusiasm to the task)for a policy which suited us.
Luckily we have the $5000 and when all's said and done, if it's your children's health that is at stake all that you care about is them being well again. If I read this post I would say "silly twits they should have sorted it out before" (I still think that) ... this is a lesson very well learnt for us ... "he who hesitates is lost".
Like I said ... get the insurance, or invite responses here for people who have decided not to and have got away with it.