EDIT: The thread title should read "... xfer desktop routes & waypoints to PDA?"
I've tried Garmin Mobile XT (v4.10.10w) and TomTom Navigator 6 and while both seem to claim that you can transfer routes and waypoints from their respective desktop software (Mapsource for Garmin and TT Home for TomTom), I still haven't been able to do this.
So I'm wondering if there actually is any decent GPS software with a PC desktop component that will allow the transfer of routes and waypoints to the PDA navigation software - is there?