I was invited to a club to shoot some models there. I'd never worked with on-camera flash (preferring remote strobes) and I was unsure of what I'd get.
Naturally, my flash unit failed within the first flash, and I had to rely on the built in one on my Fuji. So for running live, with no experience, I was pretty darned nervous, fortunately the club was nearly pitch black and much of the flash was lost in that, so the models turned out well, as you can see here.
I'd dearly love a bette flash unit, but the prices!