DS 4 has been in a play based preschool since 3 and has enjoyed it. Academically there is no fit (but that would have been near impossible anyway)but he has really developed socially, become more independent, learnt about school readiness (ie sitting listening in a group etc, show and tell) and he loves to play as much as he loves to learn. It is amazing how some of those "sloppy" things improve with some friendly competition!