About a year-and-a-half ago I was finally forced to make my own decision about the leaking rear air suspension on my '93 LS400. I just couldn'e see going the full Lexus-Dealer route, just way too much money for a car already 12 years old (at the time).
Soooo ... I went with the Strutmasters conversion kit (http://www.strutmasters.com/catalog.php?cat=14) which I believe ran me about $795 to have the struts delivered, and (damn, I don't recall exactly) perhaps about $250 to have my mechanic put them on. He said that it was all pretty straightforward, EXCEPT we was never able to make the "AIR HI" light inoperative (he said the CD-changer was in the way, and he couldn't get to it the way the instructions said). Now I have lived with this idiot light blinking on my dash, which has really been no problem for me.
THE RIDE? Not as good, that's for sure. When the air suspension was all working the car felt good, but now it feels rather, err, normal, if you will. I recall the first day taking it for a ride after the conversion and feeling really let down, especially after talking with the guys at Strutmasters for so long with concern at how the car would ride afterwards: "You'll be absolutely thrilled with how great your car will ride," they said. Well, I'm not, but ... what can I do about that now?
The other thing to note is that, of course, I couldn't keep my front, fully functioning, air shocks and just convert the rear, which was the only problem. Now I do have a working set of front air shocks that may be worth something to somebody. Y'all contact me (cliffordjames@hotmail.com) if you need 'em and make me an offer; I figure they are easily worth $400 plus shipping for the pair (as I've seen them go for twice that on eBay).
So, that's my experience.
Of course NOW my dashboard lights have trouble coming on, sometimes only coming on ten minutes later, after flashing on and off for a while. PLUS, when they do come on the odometer and speedomoter sometimes simply won't function ... still, all in all, I like this car. I like how understated it is, and other than those things mentioned (oh, and the freakin' power-steering pump), it has rarely been in the shop in five years, so ...
... there ya have it!