Your circumstances are a bit more specialized than mine with your use of the radio controlled triggers. There are two other circumstances I’ve encountered where higher speed flash synchronization really helps:
Extended range fill with bright sun
Fast action under artificial light (on-camera flash)
The 1 stop x-sync electronic shutter speed advantage of the D70 provides about a 40% range advantage over the typical mechanical shutter limit of 1/250s. This can help when reaching across a pool or photographing your kids playing out in the surf. Even when the subject range is close enough using 1/250s, the flash does not need to fire as strong for a given distance when using 1/500s, so the flash can recycle faster.
Nothing freezes fast action motion like an electronic strobe. But for camera mounted flash one's going to get that deer-in-the-headlights lighting effect. Sync speed isn’t a big issue if one can hang lights or mount additional side lights to cover an event where the flashes are the dominant light source.
However, that’s not a practical option for a parent trying to get a nicely illuminated photo in a gym, or under field lights outside at night. You’ve got to take advantage of the available light and augment it when all one has is a single camera mounted flash. A shutter speed of 1/250s works for some conditions, especially if you’re trying to capture motion blur. But I find 1/400s more often works better.
I’ve found that in some gyms I can bounce off a tall white ceiling and achieve uniform lighting in reasonable balance with the available light. There’s no way that’s going to work with FP sync, unless I gang about four SB-800s together.
With the D300 and especially the D3 there is hope that I can dispense with the flash altogether and rely on their greater sensitivity and dynamic range to handle the poor lighting conditions found in elementary school gyms and municipal baseball fields. I’ll just have to get better at dealing with color correction. (Many of those artificial lights are constantly changing color during the electrical line’s AC cycle period, so preset WB isn’t a complete answer.)
When I first read about live preview for the D300 and D3 I thought they must have some sort of electronic shutter capability. Apparently it must not be fast enough -- like an interline CCD. My hopes where dashed when I read further into the specs and saw the old 1/250s second limit.
... and i dont choose to
use nikon flashes anyway (not enough power).
I'm curious. What flashes do you use?
Steve
. 
)