I've always used a secondary for all of my beers. I think it makes a big difference in the clarity and gives it some time to condition. I always have a ton of sediment come out of my beer in the secondary. It doesn't seem to matter if it was extract or AG- I always do it the same way.
I follow the "1-2-3" rule- 1 week in primary, 2 weeks in secondary, 3 in the bottle- drink! I usually leave the beer in primary more like ten days, though- just because of my work schedule. I usually bottle about 3-4 weeks after brew day.