Bought the car new. Under warranty, EGR valve replaced at 2,000 miles and replaced a rear window motor at 16,000 miles. Mechanically, the car treated me well. I changed the oil/filter every 3,000 - 3,500 miles and general fluids a little sooner then required.
As I said, mechanically the car was good. Electronically, it was a little troublesome. My biggest issue was that the ABS, traction control and a intermittently. At 5 years and about 42,000 miles, I took the car to my independent mechanic of 18 years. He told he couldn't troubleshoot the problem because only GM had the equipment able to do so (this coming from a well established independent mechanic in business for 38 years!).
Took the car to the dealer and was told the ABS module and pump was bad (hence the warning lights) and needed replacement... at $2,200!! I moaned that such a part shouldn't require replacement at only 42,000 miles.
Too make a long story short, I contact the Buick rep in the area and they agreed to reimburse me for the cost (kudos to Buick for stepping up OUTSIDE of the warranty period). On the other hand, 18,000 miles late, the same thing occurred with the same diagnosis. At 59,000 miles, I opted to sell the car to a dealer for $5,000 then put $2,500 into a 7 year old car (cost of the parts/labor went up 10%+ in 16 months!).
All in all, back in 2000 it was the best bang for the buck for a car purchase. Loaded, the GS cost me $24,500 + TTL. Aside from those electronic issues, the car was good. Seats could have used better lumbar and lateral support. The interior was ergonomically correct, good size trunk and could seat four in comfort; five for short trips. I now own a Lexus GS and wrote a report on that in the appropriate area.