I use a TomTom as well. Occasionally the GPS will take you to the wrong place, so its good to have a knowledge of where you are headed generally. My sisters house is in the middle of a bunch or cornfields 15 miles from Rockford Illinois - the GPS takes me right to her driveway, so its most often the best tool for the job (I could never find it on my own). I often have to enter Long/Latt coordinates (I get them off of Google Earth) to pick the places I drive to in the Colorado mountains - The TomTom has obscure 4WD trails included.
My only gripe about the TomTom is that if you upload an updated map, you lose all of the 'favorite' locations that you entered. Re-entering them can be a pain.