I know about the SU-800, but I don't even think that is needed if one uses an SB-800 with the D50. However, I haven't tried it yet with a D50 since I haven't picked up a second Speedlight "yet" though I have used my D200 in the Commander Mode to trigger an off-camera SB-800--very easy to use.

I tried out the Hasselblad H3D-39 when I was visiting Samy's in LA. A nice camera though I'm very glad I didn't purchase one even if I could afford it then since the price has dropped around $10K since I looked at it after RCX.