Bought the Sonata almost 3 years ago and now have 55k mostly highway miles. Travel about 80 miles/day for work. The cloth seats are some of the most comfortable non leather, non premium seats I've used. Nice thoughtful interior. It has so many upgrades that have trickled down to a base car over the years. The ac and heat are fine although climate control would be nice. The XM is a feature that I use regularly and enjoy. I have done nothing to it except regular maintenance and a new set of tires. I average about 30 mpg going 70-75 on the highway.
The full size cabin and trunk. the seat comfort, XM radio, reliability, and the overall value of the vehicle. I paid $16,500 for it new and it has cost no money. Considering the mileage I get and I'm able to write off the mileage, its a money maker.
Only 3 - the suspension conveys the bumps on uneven surfaces more than I'd like. The acceleration on ramps could be better and the handling could be more taut.