What's the one remaining thing a standalone GPS unit can do that Google Maps can't? (Besides work offline) Lane guidance.
Right now, Google Maps would best be described as "Turn guidance." It will tell you when to make a right turn, but that's about it. Lane guidance is a step further: Your next exit is coming up on the right, and a TomTom (pictured) will better prepare you to make the exit by directing you to the right hand lane in advance.