Well, I CAN confirm that mine works for updating waypoints and routes... I've not used it to transfer mapsets (I use the automotive kit with my GPS196 that requires add-on detailed mapsets) as the transfer is limited to 9600bd so they take HOURS! I use the USB datacard programmer for this instead...
Mine is marketed as a PDA adapter... it's a Belkin F5U109. Was about £30 from Dabs.com, I think...
Belkin PDA adpater
Was reco'd by another PPRuNer on the 'Pooter Issues thread, so I can't take finder's credit!
Good luck!
Hersh