Yup. I have only recently felt the urge to see how the Nikon D90's Flash Sync actually perform in conjunction with my Nikon SB-400 Speedlight. Obviously, my kids are often the test subject.
As it turned out, the fastest speed I can engage my Nikon D90 is 1/200 second, implying intended subjects should not be too fast to be captured in those low-light conditions. Again, my Nikkor 50mm F/1.8 made my day in the above shot.
Enjoy!