I have driven my 2005 Cadillac STS for 12 months and find that it meets most of my expectations. Coming from a 2002 BMW M3 (and a BMW 540 prior to that), I was looking for more room and creature comforts. Wishing to buy American, I chose the STS V8. I have had only one signifcant problem, the steering column came loose after two months apparently from a manufacturing defect. Cadillac replaced it promtly and I had no further problem. Overall, this car is a great combination of power and a smooth ride, with useful technology (navigation, remote start, and terrific sound system-you must listen to 5.1 channel musice CDs in this vehicle). All this and it's American!
The power avaialable at all speeds, great ride, cooling fans in the seats, technology (especially the Bose 5.1 system!), and quality of build / fit and finnish.
The fuel economy averages 15, and have not seen more than 20. The tires inadequate for power (lousy in wet weather). It is short on room for storage within driver's reach. the heat in steering wheel should does not extend through the upper wood portion. It could use an extra 2 inches of leg room in the rear for adult passengers.