The primary criticism of the Bjorn is that the baby hangs by its crotch.... carriers like an Ergo or Beco have the baby in a seated position that distributes its weight more evenly. For that reason I wouldn't use a Bjorn a ton. Once in a while, especially in the early days, is fine IMO.
Baby facing out has its critics too... again, it's how weight is distributed. It's tougher on your back and it's tougher on the LO's hips. There are also people who say babies get overstimulated when facing out. A facing-in baby has the option to lean on mom's chest or of hiding his face; a baby facing out can't do those things. It's another case where I'd say a little is fine & even probably fun for the kid, but using it a lot isn't the best idea.
For $20 I'd try it, use it for fun once in a while, and eventually sell it and get a more supportive carrier.