Let me put it this way, I don't want a whole nother book's worth of demons, devils or celestials. Modrons, formians, slaad, and other neutral outsiders could use a book, but first I'd rather see creatures that are from the Material Plane and are not created by magical experiments. I just think those are easier to get use out of in a non-plane-traveling campaign (and I assume most games don't constantly deal with other planes).As I stated before, I can see some call for an "outsider" book, but I think it should be last since outsiders are overrepresented right now. However, when such a book is done, I think it should stay away from the obvious. I think it should, at best, brush on demons, devils, archons and the like. It should focus on the neutral outsiders and the good/evil outsiders that don't belong to a group that's been covered in books like BoVD or BoED.