I bought a Manduca when my son was 3 months old. I'm very happy witb it! It's very easy to put on, doesn't hurt my back or shoulders at all even though I already have back pain from lifting the baby all the time. I definitely recommend it, esp. if your baby is older than 3-4 months. It has an extendable back, which I keep folded indoors so my LO can move his head and look around more freely, and I extend it when we are outside so he gets more support and safety. Also has a hood and you can cross the straps at your back.
I wouldn't use this with a newborn though, even though it does have a newborn insert. There are much better slings for newborns, like the Caboo mentioned above. I also recommend going to a shop where they know a little bit about baby carrying and you can try on different carriers with your baby in them just to see what you and your LO like best.