lol nugget, this will be a long discussion............
but a very good one. there are some great threads and discussions here from the past. i will try to dig some up for you to read if you haven't already.
very good replies by ef, chip and perry.
i use them, but the key is when to use and not (management and sometimes timing) or your personal preference.
i don't like queens laying in my honey super frames. this darkens the comb. yes, you can move her out and down, put the excluder on, the bees take care of the brood, but over time the frames she has laid in darken.
also, i use a top and bottom entrance so when an excluder goes on the bees have access at the top rather than always taking a field trip up through the hive from the bottom.
and like perry said, do not use an excluder with any undrawn comb/foundation. this is a great hindrance. put the undrawn comb/foundation in, feed til it is drawn (do not rely on a flow) and then decide whether you want to use one. typically when there is a honey barrier in place, the queen will not cross this to lay in the frames or the boxes above.
EDIT AND ADD:
the best time to get bees to draw comb is in the spring of the season. you can put them on just before the flow starts, and feed. if the flow is a decent one, between the feed and flow, the frames will get drawn rather quickly.