Coming from a 2010 Audi A4, which I loved to drive, but was constantly in the shop for issues, the 10 year, 100,000 mile warranty was one of the first things that caught my eye. I'm coming up on my 3rd year in my Kia (purchased new, March 2012) and have more than 60,000 miles on the car and have only had one minor issue, so the extended warranty is peace of mind at this point. At about 25k miles, the wastegate actuator stuck in an open position -- this is a known issue (TSB issued) and was fixed once and hasn't been a problem since. It's the only repair I've had for the car. I replaced the original tires at about 42k miles, but moreso because one was destroyed by a pothole. I probably could have gotten another 5-10k out of them. I'm still amazed at the brake quality. 60k+ miles and I'm still good with the original pads and everything.
The German-inspired styling of the car initially caught my eye. After I purchased the Optima SX, I got a lot of positive comments from friends who wondered what the car was (Lexus was most common guess). Very luxurious look with sharp, aggressive angles and sporty rims (not the pizza slice rims that come standard on the SX, but the 8-spoke 18" ones).
With two growing boys, backseat room is a necessity. The Optima has a TON of legroom in the backseat... adults fit comfortably with deep seats allowing for adequate headroom. The perforated leather seats are comfortable and wear well. The model I have has heated seats front and back and air conditioned seats in the front. Mine also came equipped with back-up camera, navigation, and bluetooth integration. The back-up camera works great and the guide lines are invaluable. The navigation is good -- doesn't always pick the best route, but it's easy to read and use, and it always gets me to my destination. The passenger can program it while the driver drives and the annoying voice directions can be silenced-- nice feature that other cars don't allow. The bluetooth works well with my Android phones, although sometimes it doesn't link to the phone automatically and I need to manually link them. Once linked, it works flawlessly. Gauges are clear and easy to read. The ride is tight and sporty (so you'll feel the bumps in the road, but nothing too jarring.) One area Kia whiffed on was noise reduction. The car is quite loud at highway speeds, but the quality sound system drowns most of that out, so it isn't unbearable.
This is my biggest (and only real) complaint with the Optima. It advertises fuel economy of 22 city, 34 highway. I drive a lot (100 mile round trip daily, with more than half of it being highway miles). Admittedly, I have a heavy foot, but I regularly get about 24-25 mpg combined, with the car in ECO mode. The best tank of gas I ever got was a little over 28 mpg. (I calculate it manually, don't rely on the on-board MPG estimates, as they are always 3-5 MPG more generous than reality.)