We bought a slightly used 2003 Century for my wife. It now has 59K miles on it (in 2010) and has not been high maintenance at all. She really likes the car. Beyond routine maintenance, I do not think that it has required any other care. However, it is garage kept and locally driven mostly. The exterior has a timeless quality about it and still looks up-to-date (at least to me). The interior is a mix of cheap materials and upscale features, but overall functional and attractive. Several years ago, we did have a problem with it refusing to crank. Never did determine what the issue was, but it has never reoccurred. For the price, I recommend the car.
Nice styling, "affordable luxury." Low maintenance, smooth ride, family friendly. The V6 engine is capable, but not peppy. Just seems to be a solid car. I trust it more than the 2003 Buick Rendezvous that I drive.
For a car that is so cost effective, it is hard to recommend improvements. Just keep it maintained properly.