The STS is beautiful to look at, comfortable to drive, and you couldn't ask for more speed. However, the handling leaves a lot to be desired - I've driven trucks that corner better. But, the worst feature of the car is it's absolute lack of reliability. The car is in for service several times each year. Some items have been repaired multiple times. The problems are both mechanical and electrical.
Highway performance and comfortable interior.
Build things correctly so that they don't break down.