If you can help it, shoot your flash behind you, not at your subject. It helps make the shot look more natural, rather than like you're blinding them with a spotlight.
Here, I bounced off of the ceiling behind me to the right with a fluorescent green gel (in an attempt to match the horrible lighting). The flash didn't have enough time to recycle for the second shot. They're both the same exposure, as you can tell from the background (and the EXIF data). The only difference is the flash.
Also, wide aperture wasn't responsible for the background blur - that's from standing back far, and zooming in. Watch the first 3 minutes of this for an explanation and demo:
www.digital-photography-school.com/blurring-the-backgroun...
Shot with: 5Dmk2 with 70-200mm and Canon 580EX
If it had been a 430EX, I would have had to bounce it over my left shoulder :)