J.R.
Honestly, when my baby was first born, I couldn't really breastfeed using any sort of carrier. I always felt that I was either going to suffocate her or twist her neck. Thankfully, she was light enough that I could hold her in my arms and walk around with her while I nursed.
Now that she's older and has better head control, I am able to nurse her in the Bjorn. I just have to keep it low enough so that her face is at the same level as my breasts. I do have to maneuver a little to get the nipple in her mouth, but once she's latched on, it is so easy to just walk around with her like that. I put a nursing cover over the whole shebang, and no one can tell. I wish I had figured out how to do this with my first, because it has made my life so much easier.
I know other moms who were able to nurse their kiddos while carrying them in an Ergo. But, again, that's not until they are a little older.