I had a mates 430exII on the camera, bounced to the roof (at all angles throughout the night, I was switching between portrait and landscape orientation and ended up with the flash at weird angles just to get some more interesting light bouncing from different directions) and I had a coaster held on the back of the flash with a rubber band as a bounce card to give some fill-in flash.
Settings were approx f4.5, iso800, 1/25-1/40, flash at somewhere between 1/16-1/32 power, depending. The thing I'm working on each time i go out (this is the 4-5th time shooting night-life with a flash) is getting enough ambient in to balance the flash, and try to get cool light trails happening (lighting at this party wasn't interesting though).
I'm not amazing at explaining, anyone who read my tutorial on making a camera bag a few pages back would agree, but hopefully that made sense. I know what you mean about (not) subtle flash, you should be able to solve that by slowing the shutter, setting 2nd curtain sync if you can, and lowering the flash power