If you are looking for a soft, luxurious Cadillac-style ride, you won't find it in the STS. Its bucket seats are pure Mercedes stiff. I have moved from a 2004 Jaguar S-Type with the Sport Package to a 2006 STS V6 with the Performance Luxury Package. I love the STS and all the technology. The STS feels more luxurious and larger. It has great ride, is quiet, and has no road vibration - but the seats are so firm that it ruins the ride. The lumbar support is too hard and does not fit a 6'2" body. The Jag S-Type rides softer on the freeway and tighter winding roads. I love many things about the STS, but a 1-2 hour drive is all that I can stand.
All the luxury technology - including the remote start, GPS, XM radio, tri-climate control, and Bluetooth.
Fix the seats! Put in bucket seats that can adjust from firm to Cadillac-style softness. Add a wider range on lumbar support.