I bought my Sonata GLS new in the summer of 2001. I have a 43 mile one way commute to work. I change the oil every 3,000 miles. I replace the engine coolant and transmission fluid every 60,000 miles. I replace the timing belt and serpentine belt every 60,000 miles. My reward for taking care of my car is 300,800 miles so far. My car does not use any oil or leak any fluids. I've had work done on the AC system once and had it charged a second time. I replaced the front wheel bearings once and each of the front tie rods once. Eleven and on half years of reliable service sums up my satisfaction with Hyundai. btw, This is the first car that I have ever kept past 100,000 mile.
I don't really have any specific favorite features.
I have some rust on the body; but after 11 Illinois winters it is not excessive.