Two cents more:
 
I don't see the need to clip queens, though it appears to be common
practice with many folks.  At best it might cause a swarm to return to the
hive for a couple more days, when it could leave with a virgin.  Looking at
the "big picture," however, by the time a colony has so many swarm cells in
development that it is going to swarm, there are more siginificant
physiological changes that have already occurred in the colony.  The
queen's laying tapers off, there is reduced foraging and storage; normal
activities begin to slow down in general.  If, on the other hand, swarm
control measures are taken before this point is reached, the colony remains
in a state of high growth/production.  In my experience this means taking
control measures (removing brood a/o bees) at about the time when eggs or
young larvae start to show up in queen cups.  Rather than just mash them
and reassemble the hive, take it as a symptom of the underlying condition
of the colony and take measures immediately to remove the congested state
of the brood nest.  I have sometimes worried that I took too many bees or
frames of brood from colonies at this point, only to return to find them
working with new vigor and collecting honey in quantity as compared to
colonies not so treated.
 
Clipping does have the advantage of helping you to determine whether a
queen has died (or left) and been replaced.  I'm not sure about the pro's
and con's, supersedure-wise (i know some of the animal rights crowd have
even expressed disdain for the practice of clipping!) but I'm quite sure I
am too clumsy to make a regular practice of it without queen injury.  So
it's never become part of management for me. Additional info on this topic
would be interesting.  Anyone?