I've probably come in a bit late on this - but what the hell.
My nephew, who is now 9, went to a Montessori for his first 2 or 3 years of education. He didn't get on with it at all. It seems that it was very much about learning and not enough about having fun and playing. It could have just been the particular one he was at.
I am very interested in sending my daughter to a Steiner school at least for her primary years - but the difficulty is that they are so few and far between. Two friends of mine (adults) are products of Steiner schools and say they are fabulous for the first few years as they focus on motivating children and building up their self esteem. The down side is that they do not focus on academic achievement at all - these friends had to have extra tuition at 'A' Level standard.