I used to feel Steiner was quite a benign system, but having had close contact with my cousins children who go to Steiner schools (albeit in Germany, where it's more of a mainstream choice) I've changed my mind.
I think there is quite a culty philosophy around it, which they're not very upfront about, and which very strongly informs the teaching. I also think that for a bright child (which my cousin's children are) the late introduction of reading and writing can be damaging.
Her oldest is now 8, can't read, write or add up, and since they're not allowed videos, TV or story tapes, has no input in terms of ideas or thoughts other than a diet of fairy stories and myths which manage to be simultaneously violent and quite twee. The artwork they produce didn't strike me as particularly creative, rather as quite stylised and instantly recognisable as Steiner.
In comparison with my dd1's classmates here, the Steiner children come across as very self-centred and immature and not very well socialised, either with other children or with adults.
Personally I now feel I would not consider Steiner unless I had a child with very particular needs for whom the State sector was demonstrably not suitable.