I have both a 2004 LS430 and a 2006 LS430 with the Ultra Luxury package.
The 2004 has been great, one problem is 45,000 miles (backup camera) that was covered by warranty.
The 2006 has been a big disappointment. It was delivered with several inoperable components (mainly due to missing fuses) and has long term problems with squeaking door trim and a moonroof rattle that several visits to multiple dealers have not fixed the problems. Also, the radar cruise control failed and was repaired under warranty. No problems with the air suspension.
I would recommend as 2004-2006 LS430 without the Ultra Luxury package. The package adds a lot of complexity to the car, with little benefit. Looking for the Ultra Luxury package will limit your choices since i don't think it is very common.