As usual, i am on the other end of this good discussion.
What good does QT do if the system isn't as good as the reef system? It needs to be even better and nobody does that. All you will do is stress a fish that is already stressed and that produces disease. So in some ways, the only reason to have a QT is to make it easier to catch and treat a fish that is dying because of the QT tank. A healthy fish brushes things like ICK aside, it can't penetrate their slime coats and believe me, any system that hasn't got strong UV filtration has spores of ICK and other parasites as well as loads of bacteria in it.
If a fish has been at the LFS for some time, I don't flinch, I do a 3 hour drip acclimation, look at him under a powerful light to see any lost scales or obvious parasites, then just a few hours before dark, I add them. I have lost fish in the last 20 years, but the cause was water conditions setting off a disease outbreak. Weak fish get sick.