I've used Garmin, Magellan and Tom Tom. I like the Tom Tom best for the features and menu options. I use it often and am familiar with the menus. The Magellan is the easiest to use and my wife prefers this one due to the more intuitive interface.
Now the Garmin was a cross GPS - car and hiking unit. It might seem like a good idea to have hiking GPS that you can pop out of the car while it is on the store shelf. It isn't - trust me, holding a plastic block up into the trees to get signal? Not cool. ALSO, the Magellan GPS liked hiking so much, it actually broke my truck passenger window in a Baltimore parking garage and went to find the Apalachian Trail. I haven't seen it since - DON'T LEAVE YOUR GPS IN VIEW (even an old one), especially in Baltimore.
I know - wah, wah, wah - but I have to say, buy these with lifetime maps. All these companies are a rip off when it comes to buying an update. To me, map updates should be free, especially since they are now plugging business info into them (ad $$$).
Traffic updates - critical in the Washington DC Metro area where we have the biggest long term parking in the world - I495.