My little guy is only 6 weeks old, but so far I really like this tub. I only used the sling until he was about 4 weeks old, but he was a 9 pounder. Smaller babies should be able to use the sling longer. His butt did seem to hit the plastic part in the middle while in the sling, but probably was due to his size, and it seemed to bother ME more than it did him! Now I am using the infant reclining part, and it's working out well. I use the tub on my bathroom sink counter, but he's already learning to splash, so will have to move it to the bathtub SOON! Haven't used the toddler part yet, so can't comment.