My baby hated the Bjorn, and most other carriers! He's a picky guy. He also hated strollers, so we had to get a good carrier. My friend with spinal arthritis recommended the Ergo, because not only is it better for baby's back, but it is much better for Mommy's back as well. My son LOVED it, and used the Ergo until he was four and a half comfortably, because it is designed to grow with the child. It also allows the child to be in three positions: front, side, and back, and it took about 5 minutes to change from one position to another. I carried my son every day for years in that thing, and it is still in great condition for #2, when he or she arrives!
There are three drawbacks to the Ergo, as far as I have experienced. One, I am a big lady, and the waist straps barely fit around me. There is an extension available, but my vanity wouldn't allow me to buy it, so I had to wear it tighter than I might have if I weren't so big. Second, although it is easy to change the straps positions, it does take some getting used to and was hard at first to figure out how to change from side to front seating position (or front to side) and figuring it out in a public restaurant with a fussy baby isn't fun! So practice at home lots before you go out.
Third, putting Baby in the Ergo on your back is quite difficult by yourself. I tended to keep my son in front or side position if I didn't have a helping hand to make sure I didn't drop him.
Like I said, none of these things in any way makes me want to get a different carrier for #2. In fact, I am planning to get an infant insert this time so I can start using the Ergo from day 1 this time. I highly recommend it, for the health and care of child AND mommy's back.