I'm pretty partial to my nüvi GPS receiver from Garmin because I've always preferred the nüvi's maps and user interface design to that of their competition. One thing that's a boon for Mac owners is Garmin's beta Project Bobcat software for Mac OS X that was announced in January and was recently updated to version 2.0.0.8 in July.
Bobcat makes your life much easier by allowing you to transfer waypoints, tracks, and routes between your Mac and your Garmin device, manage your data using your Garmin maps, search for points of interest from the convenience of your Mac then sync them to your GPS receiver. Bobcat is also excellent for removing erroneous and duplicate entries in your Favorites list and for fixing waypoint typos that you never get around to.
Bobcat is another great reason for Mac owners to love the nüvi.
What's your preferred automotive GPS receiver these days? Why?