It has been the best car that I have ever owned (of 11 cars/minivans). My wife and I enjoy it so much that we bought a 2012 Sonata Hybrid with the leather package so that we can both drive a Sonata hybrid.
Safety - This is the highest importance.
The car has excellent crash safety ratings.
More important is that it handles/maneuvers extremely well. It has a large amount of power to get you out of danger fast: passing, merging into traffic or accelerating rapidly from a stop to avoid a distracted driver who is barreling into an intersection. Shifing at low speed is smooth after initial computer update.
MPG - 42+ overall
Comfort - spaceous interior
I could not be happier with this car.
Standard intelligent Bluetooth that truly provides handsfree phone use.
Very comfortable seats - best headrest that I ever experienced
Smooth quiet ride - allows adults to arrive from a long trip relaxed and rested and the children can sleep in their carseats.
Seats 5 adults or 3 adults and 2 children in car seats or any combination.
Climate control is excellent with extra vents for heating or cooling passengers in the back.
Overall car control - maneuvering and braking are very controlled.
I feel very much in control and safe driving this car.
Proximity detection and keyless ignition work very well.
The car communicates with different chimes to tell you that you need to do.
I like to think that I that the letter I wrote influenced Hyundai to offer a leather package - so that one can get heated leather seats without having to get the entire navigation package.
Now that the 2012 comes with a leather package, I cannot think of anything else to improve.