Just a few thoughts on my 2006.5 LX 4 cylinder automatic. It has been almost exactly a year since I bought it new, with 10,450 miles on it now, and it has been absolutely terrific. No shift flare, no airbag light issues, nothing major or minor -- in other words, nothing at all in the way of issues. I follow the owner's manual's recommended service for "severe" driving conditions, changing the oil every three months, but other than that it has never seen the dealer's service bays.
I had it on a 3,900 mile road trip in August, and it gave me a very consistent average of 32-33 mpg on the highway (even during stretches with A/C running, it didn't drop more than 2 mpg from the average). My city mileage -- and in Pittsburgh, "city" literally means 70-75 percent stop and go every block or two, with chronically sluggish traffic-- my mileage depends on what gasoline I use. Oddly enough, it does best on Sunoco 10% ethanol, which gives me between 22 and 23 mpg; most other brands produce about 1-2 mpg less (especially BP).
It is also quite comfortable -- my legs unfold quickly and properly when getting out after long stints without stopping, and rear seat passengers don't look like they want to beat me up after riding back there! (I only wish the light gray cloth upholstery was a little darker -- it can be tough to keep clean at this time of year.
)
Having traded up in size from a Hyundai Elantra, I have no regrets. Hyundai and now Kia have both been completely trouble-free for me over a nearly five year history with them, and I unequivocally and enthusiastically recommend the Optima in particular.