I've had this car for 9 years now- it's been great. No major issues,a few flaws, but 1998 was the first year of the new model. I have about 210,000 km (divide that by 1.6 for miles) and I just did regular maintenance. Very confortable and quiet. As it is getting older, I consider replacing it with an Audi A8 or BMW 760i but in all honesty I have no reason other than getting a new and fancy toy. I highly recommend it (check the J.D. Power reports on Buick, both Century and Regal).
Smooth ride, quietness (it happened to me several times when I tried to start the engine when the engine was actually running), reliability.
GM should have kept the engineering and changed the exterior sheet-metal only. Cup holder ingenious but flimsy, to honk you have to press hard and I find it being a safety issue, rubber seal sticks to the windows.
† Edmunds.com received the highest numerical score in the proprietary J.D. Power 2014 Third-Party Automotive Website Evaluation Study℠. Results based on responses from 3,381 responses, measuring 14 companies and measures third-party automotive website usefulness among new and used vehicle shoppers. Proprietary study results are based on experiences and perceptions of owners surveyed from January 2014. Your experiences may vary. Visit jdpower.com.