Researched this for last Christmas - they all seem pretty good these days.
I had an old Magellan that had it's problems, but it may have been more due to it being "old" rather than anything else.
Ended up with the Garmin - they're the GPS's in planes/boats etc., so I figured they must be okay.
I'm a cheap b@stard so went with:
http://www.walmart.com/catalog/product.do?product_id=3556744&povid=cat538883-env31717-module64908-rLink2
I can't believe how much I rely on it! Great, no frills, unit.
Smart buy- you won't regret a GPS unit.
Best,
Nos