Being inspired by the Montessori philosophy for a long time now, and having used floor beds before with our older children, it was clear to us right away that we would go this way again with Elie. He has been sleeping on it since he was 3 months old. We used a double size bed at first to help the transition from our bed to his, which also gave him a very large and safe space to explore freely during the day. Once the transition was made, and E started being more mobile, we changed to a smaller size mattress to give him more space in his room.
Floor beds have always worked perfectly for us. We love how it nurtures the sense of exploration of our young children, and also how it give them the freedom to access their bed whenever they wished, by themselves. I believe this partly explains the pleasure my older children still have when it is time to go to bed.