I have a 2004 with Navi/Air Suspension (Ultra Lux) and in the 6 months of ownership have not had a single issue. I've had 2 oil changes and a in cabin filter replacement during my ownership. Car is at 86K~ and drives better than a lot of newer cars.
Although my ownership is limited I use to valet cars in college and I have to tell you that i've driven everything imaginable. When thinking of sedans I've driven M5s, Alpina B7s, S55s, S63s, and no as awesome as those cars are in my opinion they don't drive as smooth and comfortable as a LS. When looking at power alone obviously the LS can't keep up with those cars however looking at the total package as far as comfort, durability, and cost the LS wins hands down in my book.
Good luck with your search and enjoy the forums. The guys on the LS forums are very helpful.