Garmin scenario
1. Audio says "in .3 miles turn right" - at .29 miles however there is a turning to the right, but actually the routing requires you to follow the road to .3 miles where there is a sharp bend to the right which the GPS interprets as a turn - standby for "off route, recalculating" This happens very frequently
2. The road you are on bears to the right but the route you require to follow is actually another road that goes straight aheadish - the change of road will not be announced and once again you can expect to hear "off route, recalculating"
3. Approaching a large and complicated roundabout you hear "take fourth exit onto XXX street" - so round you go counting exits (not to be confused with service roads) and reading the signs. With a glance however at your GPS screen you could have spotted that your exit is the one at three o'clock and can devote your concentration on getting into the correct lane and watching the idiot in front who is about to cut you up