After going through with my daughter an ergo (which I LOVED for my son) a stretchy wrap, mei tai style carrier, bjorn style carrier and a fitted sling I finally bought a bubba moe and we (me and bub) are both so happy with it.
I think the main thing with it with the adjustable strap I can easily change her position as I find she gets very wrestless and cranky VERY quickly in carriers that have her in the one position. She can squirm, look around, suck her fingers, look at me, look out, be on my hip, front, be side on or fully facing outwards with her feet tucked up in front of her, she can fall asleep, breast feed, play - we even have a toy or dolly in the sling with her for her to gnaw on and play with - and its all very easily to let the strap out, or put it in, to shift her position, which also means its changing the weight distribution for me across my back which helps my comfort too.
Also, when she falls asleep I can unclick her at the back and then gently place her in her swing at home or pram when we are out - I keep the straps at her feet and dont leave her unattended, but its really quite a lot easier to put her down without disturbing her than a structured carrier.
And if in doubt - YOUTUBE - they have great youtube videos. They do provide a dvd when buying new, but its just as easy to youtube it on a smart phone.
Cons - I dont see myself using it for as long as I used the ergo carrier. I still occasionally pop my 3.5 year old in the ergo and I really dont see myself using the bubba moe much after she's 10kgs. But its been fanastic so far (newborn-4 months & counting)