I use a D1X (although I still have an F5 which looks very attractive sitting on a shelf gathering dust!).
I am a keen macro photographer and used to use my SB29 macro flash with my F5 extensively. I am baffled why Nikon have built the D1X in such a way that it is not compatible with most of their flashguns except in manual mode (other than the ones released sprecifically for the job - the SB28DX and SB50DX etc).
I am forced to use the SB29 in 1/4 power manual mode which means I lose all benfits you would expect with TTL 3D matric metering.