I've upgraded from the BabyBjorn to the baby backpack.  First, I tried to stick her in my old high school backpack like a mashed up lunch or a protractor, but then I found out you have to use a special baby backpack, one made to fit a baby.  This is so she can kick off her socks when her her feet can dangle and her hat can blow off while she is behind you and you only find out after you have hiked on the trail for the last fifteen minutes and you then have to check her for ticks and clinging critters and backtrack down to where the hat blew off, which is a patch of poison oak and when you do, you have to figure out how to bend down and pick it up.  But when I do, I turn around and she has a huge smile on her face, so its all worth it.