D80, 85mm f/1.8 @ f/2.8, 1/125s, iso800, SB-600 flash pointed up and to the right. My wife tickling our daughter on the couch.

The 400 would have worked too, but you can tell the light is sorta coming from the side to give some texture and 3D look, which I like.
This is nothing special here, but this is the D40 with the 17-55 and SB-400. The flash head is pointed straight up and going to the right, bouncing off the wall, and then coming back.
Now here's the stumper. :mrgreen: The D80, 17-55DX @ f/2.8, and SB-600 pointed up and to the left. You can see the light bouncing off the wall/ceiling and then coming back down on her face, and how the light fades towards the back of her head. If I had used the SB-400 though, and rotated the camera a bit more counter-clockwise, I think I could have gotten just about the same shot with less hassle, and might have liked the composition a bit better too.
Anyways, it's a crap shoot and style dependent too. I "say" I use stuff a certain way, but I end up swapping stuff out and mixing things up a lot too. Different tools used different ways let you shoot differently, and keeps a varied and interesting look to your photography. Just think of it this way. An SB-400 and 600 combined cost less than one 800 and do a lot more, so just get both.
