I'm a relatively newbie to competitive cycling, but I've found there to be truth in the statement "go slow to go fast". However, it specifically applies to cyclists such as myself who have a greater proportion of fast twitch muscle fibers to slow twitch. For cyclists that already have a greater percentage of slow twitch to fast twitch fibers, going slow will be of much less benefit to increasing aerobic speed.
With one race and half a season of real training under my belt, I now know:
Hills are not HILLS (bumps in Louisville won't prepare you for a race with a cat 3 climb and 3 cat 4s)
Don't ride to another city and back, covering considerably more distance than you ever have before... on a dare.
When turning left at an intersection, don't look over your right shoulder.
All's well that ends well. I'm looking forward to 2008, my first whole season as a competitor