You should never point the flash straight at the subject if that's your sole light source, very ugly. However, you don't need a huge amount of flash power to get good results bouncing a flash. For inside shooting, and I do this a lot, my typical exposure would be f/4 @ 1/15th to 1/60th of a second at either ISO 400 or 800. The flash has to be set low enough that it doesn't over power the existing ambient light.
Here's a typical wedding reception picture, nothing fancy, I just happened to have it on my desktop.
With this shot, the flash exposure is f/4 @ ISO 400, hardly anything. I kept the flash head at 45 degrees, and used the nikon flash dome to diffuse it. That way you get the bounce effect, but still have directional light on the subject. Just bouncing the light can be problematic, as the flash will pick up whatever colour the walls are, and make your colour balance a nightmare. Also, in this picture, the walls are dark brown, so they probably wouldn't reflect that much light anyway. The other thing to keep in mind is that if you're bouncing the light off the ceiling, the direction of the light will be coming from directly overhead, which will give you harsh shadows on the face, especially under the eyes.
David Buzzard 
Linear Mode
