I have previously owned a 2002 Buick Century and before that a 1999 Olds Cutlass. I have found the LaCrosse to be a decided upgrade. The 3.8 liter engine is superior to the 3.1 (although not the gas mileage), the ride is firm, ultra-quiet, and luxurious. The sound system is superior to either of the previous two cars, and the interior amenities far better. In addition, people have commented as to how stylish the car looks, which never happened with the Century ("stodgy" was the word). Within 1000 miles, I have already recorded 29 mpg twice on trips of over 100 miles. The doors fit "tight." I hope the vehicle doesn't depreciate like older Buicks are known to do.
The ABS anti-lock brakes, traction control, and the "On-Star" system are very important. The 3.8 engine is "tried and true."
Glove box is too small. "High beam" headlight indicator on instrument panel needs to be "different" in color than other indicator lights to be more noticeable. I have had the brights flashed at me by several cars, because I didn't realize my brights were still on.