The Hyundai Sonata Hybrid is the best package of attractive styling, smooth handling, excellent mileage and comfort among hybrid sedans in the US.
I found with slight care its easy to get over 40 mpg on the highway and overall 38+mpg.
Features that reduce the mpg are using heated seats and interior heater in the winter or full AC in the summer.
However, using the "econ" feature with the heating/cooling one easily achieves 38 mpg overall or better.
The jitteriness at low speeds was resolved with the first service when the computer system was upgraded to remove some of the hesitency between use of EV and gas engine modes.
Update is free and resolves issues raised in some initial reviews.
Comfortable seats - the headrests are the best I have ever experienced
Smooth handling and braking (after initial computer update)
Good gas mileage - using cruise control I got over 38 mpg overall and close to 45 mpg on the highway.
Environmental controls are intuitive and work in an intelligent fashion - in the "auto" mode the fan will not run at high speed until the engine has heated so cold air is not circulated when you want heat.
The venting for the rear seats keeps our grandchildren very comfortable.
The trunk, though smaller than the regular Sonata trunk, is very functional.
Really very little - My only suggestion for improvment is to change the fabric used to one that cleans more easily.
The leather is excellent and I would get the leather package, which we did with our second Sonata Hybrid.
I want to add that if you are considering purchasing a Sonata hybrid that I had an excellent purchasing experience from Rick Case Hyundai in Bedford/Cleveland, OH.
The dealer was interested in what I needed, not what they were trying to push.
They treated my wife and I with courtesey and respect.