I would alter that to the things passed around through forums, LFS and uneducated rather than any kind of wisdom - ignorance is bliss! ;)
I agree, although there is A LOT we can do to ensure smoother introduction and transfer. Number one is QT period. It's an opportunity for us to get them fat, healthy and ready for battle! They get used to the kinds of food and times we feed, along with use in general. Their stress levels over time in QT are greatly reduced prior to their introduction in the display. I'm also a firm believer that social acclimation is of HUGE importance and overlooked as much as QT (and the real reasons for it) are in general. After QT once ready for the display, you can put the newcomer in an acclimation container in the display aquarium, so the existing fish can "see" the newcomer and begin establishing their dominance with a "look but don't touch" approach. If the existing fish are going to be outright aggressive towards the newcomer it will become apparent very quickly as they will try to attack the newcomer through the box! Hopefully they don't do this ;) Once they've "seen" each other for a couple/few days I release them into the display while feeding the other fish and carefully watch the interactions that are surely to take place. Cross fingers, and let 'em rock! Of course as 110reef mentioned, it's imperative to have your QT still up and running to pull someone out of harms way if absolutely necessary.
REALLY?
