Magellan. I've used TomTom, Navigon, Garmin, and Magellan, and that's the one that gets everything as close to right as apparently possible (though I have not used the new maps-on-board Garmin since I'm not sinking any more money in this greedy, nasty company after that little surprise app this summer. It gets pretty good reviews, that's all I can say.) If you deal with traffic issues, Magellan is absolutely vigilant about offering alternate routes. It is constantly finding me new ways around slow traffic but, like all GPS traffic systems, you have to know whether it's truly a benefit or not. But none of the others are anywhere near as proactive as Magellan's app is.