Got a great deal on a leftover new Super ($31.7k out the door) when my '07 DTS was pulled ahead by GM. Ride has softened somewhat with break-in, but the magnetic ride control is still firmer than in my DTS. Knew I would have to replace the standard Bridgestone tires in order to make the ride acceptable. Replaced tires with Goodyear Assurance Comfortreds (235/55/18) which adds about 1/2 inch to the tires diameter and about 1/4 inch to the car's ride height. The tires made a big difference when compared to the hard riding and noisy Bridgestones. The car, at 2,600 miles, gets about 18 mpg combined vs. 20 mpg with the DTS. This may be due to the performance tuning and the final drive ratio.
MSRP about $13k cheaper than similarly equipped DTS. Same platform and factory as DTS. Quieter and smoother ride after switching tires. Rides much smoother than my '06 Q45. Seats almost as comfy as DTS. Blind spot alert system. Low NVH levels. Nav system.
Dump the Bridgestones. DTS had three seals around each door; Lucerne has only one and one-half (exterior noise more hushed on DTS). DTS and Lucerne both need the Blind Zone alert system. Update both cars for the next decade. Improve fuel economy. A six-speed automatic. Charging Ipod port. Six CDs.