As seems to be the case with other aspects of pipe smoking, there seems to be certain trends one way or the other at any given time. I've noticed (at least what I perceive as) a trend over the past couple years to drying your tobacco to the point of being crispy or near crispy. I've experimented with this and have found that I like most blends dried past the point where the tobacco will no longer stick together when pinched, to where if you pinch the tobacco you won't be able to feel any coolness or moisture. at this point the tobacco is pretty dry, but still pliant and not yet crispy. Basically, the ideal point for me (for most blends) is a step or two short of being crispy.
It varies by blend and style of course. Virginia is the most forgiving of overdrying, whereas latakia blends just get harsh when overdried. I don't even attempt to dry aromatics - I just pack em loose and smoke em slow.