I had my dd in a Montessori preschool for 3 years, she transitioned to a public school now. My ds3 just started the Monetssori preschool at the age of 3. I can't say enough good words about the Montessori preschool, and amazingly, it fits both my kids (one is the studious type, the other one an anarchic devil). But, in the end, it is only the TEACHER that matters. Follow your gut feeling about the teacher. The bad thing is that in regular preschools, teachers change quite often, you might like them in Sept, but somebody else might be there in Dec. In my experience, the Montessori school was way stable. Beware, though, my dd went through a shock moving to first grade. In many senses. The Monessori school gave her education to last her through 3-rd grade (she learns absolutely nothing in 1-st grade). But it taught her to be independent and follow what she feels like. That does not mesh well with a public school. And no, I will never regret havign put her in a Montessori preschool. I might consider following up with a few more grades of elementary Montessori school. But, again, BEWARE: I have heard parents who have bad experiences with Montessori schools, because teh teacher was in a sense or another limiting the kid. Talk more to the Montessori teacher and ask her about her phylosophy about "age apropriate" things.
