Most pros refuses to pop that built-in flash on their camera and they have an extremely good reason in not doing so. And in situation they use one, it would be an external unit flash that can be either connected wirelessly or physically to their DSLR.
The Nikon built-in flash, though compensate-ready, more often whiten the subject than adds clarity to it, all for the fact its direct fire on your subjects. Though whitened, your subjects now becomes significantly sharper but less natural looking. The ISO 3200 exposure without flash has now been automatically adjusted to ISO 200 by your camera.
To have the best of both world, the use of "bounce" flash shots is like a dream come true. And such feature can only be available in an external flash unit. So, its like a must for those of us coveting significantly better indoor pictures.