For some reason, GM's luxury vehicles have been terrible with regard to reliability.
I went from one of the most reliable cars I'd ever owned (a 1990 Buick Park Avenue) to not one but TWO pieces of GM JUNK.
I was a loyal GM person, but not anymore.
My friend owns a 2010 DTS and while the ride is very quiet and smooth, the rest of the car has been a nightmare mechanically.
I switched to Lincoln Town Car and I have had zero major problems with all three of my Lincolns.
Yes, I know it's an "old man's car", but I don't care; I'll take American-made reliability from Lincoln ANY day over a brand new Cadillac.
I've had two hip replacements at a young age (38), so comfort is an absolute must, and nothing has yet compared to the Lincoln ride OR it's reliability.