Here is a 13 minute video of Joe McNally testing out the range and application of the built-in and SB-900 flashes. If your knee jerk reaction to TTL is that it's too limited and too problematic watching this demonstration by Joe may just have you giving TTL transmission use a second look.
"Adorama Photography TV Presents Photo on the Go with Joe McNally. Join Joe in Hong Kong as he explains how to test the line of sight with a built-in camera flash and a SB-900 flash. Watch as he tests the strength of the built in flash to get the line of sight TTR transmission, and then uses his SB-900 as a commander in order to "talk" to the flash on his subject.
It is important to use a TTR transmission when taking photographs of a subject that has a large depth of field. By using this technique, you can stack the background lighting and color in close to your subject in order to achieve the photo you need. The TTR transmission will make it easier for you to capture your subject from a distance."