The appeal of the Sony adapter IMO is that it's made to fit directly with the D1 or D50. It's a high quality unit and get's excellent battery life also. The frequency response on the adapter is 20Hz-50KHz. One of the guys at the Panasonic 3CCD message board just got the D50 and adapter and should be doing some testing soon. I look forward to hearing his results.
I would like the Sony adapter but I just can't see spending $500 with I can get something like a Denecke PS-2 that is similar in size and much cheaper.