All Steiner schools are run autonomously so, just like State schools, there are good and bad. I think the best advert for any school, state or private, is the young adults it turns out into the world, and all the teenagers I have met at my DDs school are polite, well mannered, confident, keen to learn, and the academic work in the upper school is of a very high standard. If there is a school you are interested in, go along, have a look and meet the pupils.
My DD is attending our local Steiner and it is certainly nothing like any of the horror stories I have read online. Yes, the children learn myths, but there is a bit of a clue in that the children are taught them as myths. At the school my DD attends they learn about myths from all over the world, not just Norse ones. They also learn biology, chemistry, physics, maths, geography, history, English, French, German and a lot of other stuff too.
Most of the anti-Steiner comments I have read are really as stupid as expecting Catholic Schools to be teaching that at Communion the host and wine actually become real flesh and blood.
The kindergarten are even allowed to use black crayon - just to pop the bubble of another bit of misinformation I've seen.
With regard to it leading to children unprepared for the world of work, we read enough each day about how ill-prepared many children leaving state schools are. The list of ex-Steiner alumni certainly seems to show a number of high-achievers, including the ex-CEO of American Express, and of course, Sandra Bullock.