I love my Ergo carrier. It is the best peice of baby equipment I own. Forget the baby swing, the co-sleep, the baby bouncy seat, walkers, activity centers, ect... Get an Ergo. I didn't get an ergo with my first child and was always holding her, or trying desprately to get her to sleep somewhere other than in my arms. Nothing ever got done. My second child arrived just 15 months after the first. I needed my hands free. I used a Moby wrap, (I also didn't have luck with a sling). My son was quickly to heavy to wear on my front, so I started to look at back carriers. Two of my friends loved their Ergos so I went for it.
Our family loves it. My husband and I both wear either of the kids instead of taking two strollers. My son is getting close to 30 lbs at 18 months. My 32 month old also thinks it is a treat to ride in the back pack. I use it grocery shopping, walking the dog, at the mall, or just getting chores done around the house and yard. The kids never protest, and usually fall asleep.
Putting a younger child in the pack on your back by yourself can be a little tricky at first. I found that putting the pack on the changing table, laying the child on the pack, then backing in to buckle the waist belt, then putting on the shoulder straps worked slick. Taking them out is pretty easy.
My kids were to heavy to wear for very long in front by the time I bought the pack. But my friends front-wore the ergo and were very happy with it. So the ergo really can go from birth to kinder-garden.
Not only is this pack handy, it is essential.