I bought this car new 7/26/06 with 355 miles on it. Within two weeks, I made a trip to WA state. I never averaged below 25.5 MPG. For the most part, I averaged near 28 MPG. The acceleration was great. The dip stick showed little or no use of oil. I thoroughly enjoyed all the amenities (OnStar, XM radio, dual a/c, and driver memory settings). The STS was quiet and practically drove itsself, even on poorly maintained roads.
I like the driver memory positions, automatic mirror positioning when backing up, Northstar engine performance, dual A/C controls, on screen radio settings, six CD changer, and all the air bags for safety.
None so far. The car is good to look at, fun to drive, and gets good mileage.