I have a Garmin 60CSx and a MacBook Pro. Instead of booting windows I use LoadMyTracks to load GPX or LOC files to the GPSr over USB. Its been working great so far, one click and it instantly loads the waypoints. The only thing I need to boot windows for is loading new maps. For that I'm using the Beta version of vmware for Mac and Mapsource.
http://www.cluetrust.com/LoadMyTracks.html