Interesting. Just out of curiosity, what mode or other nitty gritty settings did you use on the camera so that you expose the person correctly yet under expose the background. I'm not very familiar with flashes.
To be honest, I pretty much "cheated" Camera in manual, set the aperture and shutter speed to drop the exposure to -1.5 to -2, flash on the hotshoe (gasp!) in ETTL (gasp!) and drop the flash exposure -2/3 of a stop. And you're away.
I had my demb diffuser on it for a while, but it was a bit bulky for handing to others, so it came off and went back in the bag.