I've had my STS 14 months now.I don't know what problems other people are having, but my STS has not seen the dealer since I bought it. The only thing I have done is changed oil at 9400 miles and rotate the tires at the same time. I average 20 mpg , not bad could be better. The exterior design is beautiful, although standard wheels should be 18's. The interior is beautiful with exception of cheap hard plastics on the center stack. Seats are to firm. Overall I love the car, well that is until I saw the 08 CTS. I kind of feel like I am driving an old mans car next to the new CTS.
Love the awd in snow and rain. The design, ride, handling, keyless entry, push button start. Bose, nav, bluetooth works well if you do not have the auto climate control on.
Bigger wheels, Cheap plastic interior pieces. Navigation should work while driving, voice recog needs improvement.