As one who has owned 5 Lexus automobiles, this is definitely the best one. If you are interested in a relatively trouble-free vehicle coupled with good comfort and performance and all of the "bells and whistles", the 2004 LS430 is the car for you.
I had my Benz since I was 16 till my GF got her GS300. I loved that car, smooth and quiet, powerful and sporty but lux as well. So I requested a GS430 and finally got it after 25 days, my car was imported from Lexus, Japan exclusively and now I even don't want to drive my new 2003 E55 AMG! It's smooth! It's loving! My mom has a 745ih and my father has a S67 Lourinser, believe me they never ride 1/10 of a Lexus! Of course the S67 is faster! Even I guess my E55 AMG is faster and of course M5 is faster, but even a V8 Camaro can't be seen on your miror. Go for a Lexus, it's almost 2 years that I'm driving 5 hours a day! I can't leave the car, nothing has been occured so far! Go for it! Go!
I moved into a GS430 from a GS400. Better Nav and sound but no more tiptronic transmission. I attribute the diminution in throttle response and tip- in response to the different tranny and possibly gear ratios from the 400. I have to stomp on the go pedal to get it going. GS400 more responsive and fun to drive. After the lease is up, I'm looking at the new Infiniti M45.