I suppose it depends on the subtlety of the blends in question. Some of the fellows around here are managing to describe the moment-to-moment changes in flavor as they smoke a bowl of Dorchester (ohin3, I'm looking in YOUR direction!). I can imagine that trying to do that in a pipe that's had Cherry Bomb in it previously would be impossible.
Myself, I have less subtle tobacco choices, with aromatics and latakia blends. Say 3-4 bowls of aro's (1Q, Eileen's Dream, MV-1000, Blue Note) per bowl of latakia. They all taste good, but radically different. As a result, I have dedicated a pipe to the latakia, and then I throw my aro's in whatever other pipe I feel like.
Simon