I HIGHLY suggest the Moby wrap. I love mine and I'm sure most users will agree with me. I've been carrying my 3 month old since she was 4 weeks old. The minute I put her in there she falls peacefully asleep.
I'm an active mommy that also has a toddler... I constantly have to run errands and my baby is put in the wrap while my toddler walks or is in the cart.
We also attend a class with my toddler and I can kneel, bend, sit and most importantly interact with my toddler.
I constantly get compliments on how comfortable my baby looks in the Moby wrap and people are ALWAYS stopping me to ask where they can get one.
Just like you, I have the Baby Bjorn but it was killing my back (infant wasn't even 4 weeks and already having back problems) With this wrap the weight is distributed evenly in my back and I have yet to complain about my back.
I've used it for extended periods of time and both of us are extremely comfortable. I've used it to go to the stores, class, Sea World, beach, park, walk around the block, to church and at home. What I like most about this wrap is that there's nothing in between my chest and the baby besides our two bodies. I can only imagine that my little girl is content in the wrap since she's secure, hears my heartbeat just like she did when she was in utero,
My LO loves to be in the Hugh Hold.
Downside: it's a long piece of fabric and if you wrap outside your wrap will and can get dirty. I always wrap at home and when I get to my destination I just get my baby out off her car seat and put her in the wrap.
Tough decision for you since their is other good carriers out there, some on her have mentioned a few.