I do sometimes worry that the freedom might not work well for my kids; maybe they need a bit more guidance. The youngest (7) simply refuses to do his work, and while the oldest (now 13) skipped a grade when he was 7, he failed last year because he was not doing any homework and not turning in his assignments. Stricter guidance might help them both. Or maybe not. It's hard to tell.
My parents apparently did consider Montessori for me, but I've only gone to regular schools, never did my homework, always passed, and in university discovered I had no work discipline at all, so it seems like everybody in our family is going to run into that problem at some point. Maybe it's better to learn it early.