The sole reason I do use an outline is for time sensitive A plots, where several parts all have to occur on a certain date, etc. I get too confused if I keep it all in my head.
Being the most disorganised writer I know <g>, I usually wait till I'm three quarters of the way through a story with a complex timeline before going "Eeek", rushing over to irc, grabbing my faithful beta and demanding she gets me out of the mess I'm in.

Then - and only then - do I make up a really nice, dinky little chart.
LabRat (who is sure Kae is still having nightmares over why it was night in the Alps when it should have been day...)