So the Queen has turned 90

and there has been the usual array of comments from the usual suspects. In past times some of those usual suspects would have been thrown into the Tower - and rightly so. There was a particularly snarky piece in the Guardian and another from a rabid republican here. There were other fawning pieces. And then there were a number of sensible pieces about the Queen's contribution to so many things/
Oh yes, I do have mixed feelings about monarchy. I know it is a ridiculous thing in one sense - but we need the ridiculous. We need ceremonial. We need figure heads. It gives people a sort of certainty. 
I envy people with very strong, certain, and absolute even religious beliefs. It has to make their lives much easier if they believe that they are going to heaven or eventually escape the wheel or whatever people believe. It's one reason why I would never knock another person's beliefs even if I can't see a way of believing them myself. 
But the British monarchy is more than that. It is a curious contradiction. The monarchy has no power at all and yet, because of that fact, it has absolute power. Yes, I did say it was a contradiction.
The Queen can "advise, encourage and warn" according to Blackstone - and that is what she has done. She is, according to my late constitutional law professor, an outstandingly good constitutional lawyer. (He should have known because High Court judges and Privy Councillors consulted him. I have no doubt the latter discreetly informed him of her concerns from time to time. He would never have mentioned it.)
There are specific  powers but almost all of them are unlikely to be exercised without the consent of the government of the day. (Exceptions are for things like the Order of the Garter which the monarch alone can grant - but even that is likely to be a matter for consultation.)
So people ask why bother with the monarchy? Just as easy to have an elected or appointed head of state they say.
The problem is that an elected or appointed head of state will always be a political issue. Here Downunder the Governor-General is selected by the government of the day. The Queen is then advised. As the Governor-General is also, but not solely, her representative she could reject the decision. In reality she is unlikely to do that and would only do so if the decision was an outrageous one likely to harm the people of Australia.
How the "head of state" would be chosen if Australia became a republic was a major issue during the debate which led up to the referendum on the subject. One of the many reasons it failed was the fact that people couldn't agree on the method of selecting a head of state.
The present method of selecting the Governor-General is said to be just as political as the options put up. In reality however it isn't. Both the government of the day and the opposition know that they need a good relationship with the Governor-General. Despite some protestations to the contrary the government does consult the opposition over likely candidates - just as it does for the appointment of High Court judges. Complaints of "bias" are more about politics than real bias. 
On the whole our system works well. Looking at the current kerfuffle in the United States I think I would rather stick with ours. I hope Her Majesty had a Happy Birthday.