Well, I've always sworn by pantsing before and never outlined, but I decided to do a short story version of NaNo this month and figured out pretty quickly that if I didn't have a Plan it would fall apart. So I outlined in December.
Turns out I was right. I did four stories with few hiccups. And the fifth one, the outline fell apart and now it's kicking my ass.
But I got my 50K, with days to spare, so it's still a success.