I dont use a GPS, but my missus lives (and gets lost) by hers.
I just dont trust them, if I need a route to get to a place I dont have a map for, I'll google map it, as they seem to be far more reliable. A street directory or map is the way to go, no hassles with them "missing a road" or telling you to take a 200km detour, let alone in cities where the larger buildings interfere with communication with the guidance satellites.
My sister recently got married at the Mt Tomah Botanical Gardens (up in the Blue Mountains) and instead of the GPS units (TOMTOM, Garmin, plus some dodgy brands) telling people to travel 35 minutes straight up Bells Line of Road (one single road) it sent them 75-80km out of their way up the Great Western Highway via Katoomba!
Looking For: Wreckers Saga TPB Collection (with Requiem)