I have an old-school Spyder outfit with stretch pants and a top that's mostly sweater-like with pads on the arms. If it's not too cold, I'll wear that one (or with a vest if it's colder)...
I had a lesson day with a gal at DV who was a former USST race coach. After getting me to my first gold medal that didn't feel like a fluke, she asked if I wanted a speed secret, so of course I said sure! The conversation went something like this:
Sue: Give me your jacket (my Volcom tie-dye jacket).
Me: What?
Sue: Trust me, you won't get cold and I'll be at the bottom of the course.
Me: Seriously?
Sue: Yes.
Me: Ohhhh-kay....
Ran the course, 1.5 seconds faster!!!
Ya, one race a year or two ago on the NASTAR site there was an * disclaimer that the pace setter wore a jacket.