I recently purchased a new 2008 Hyundai Sonata GLS. I was looking for a midsize sedan and the Sonata was less money than the comprable Toyota Camry and Honda Accord. I like the styling of the Sonata as well as the interior. As far as performance, I would say it is nothing special. I have driven all of its competitors and the Hyundai is a little less "stable." Meaning, it doesn't seem to be a sturdy, well put together car. Although at the same time, it doesn't seem cheap either. I have already noticed a few rattles in the car, that will probably become a nuisance.
The warranty is a big selling point with 5 years, bumper to bumper. The car is deifnitley lacking in options, but I did choose the base model. I am also a little disappointed in the gas mileage thus far.
Overall I would seriously consider the Sonata is you are also considering a Camry or Accord. It is a good value for the money and so far seems like a decent value.