You have to understand the concept of the era here. The L1011 was overbuilt - for all the reasons above, and as such she does not perform so well (in fuel / range terms) as the modern metal. However the Tristar is beautifully built. The Lockheed stable that designed her was at the time working on the Space Shuttle and that research comes through loud and clear in the aerodynamics and structure.
She is rather heavy on "old world" technology and can be a sod to maintain if you don't know the systems. But after all the initial problems with the RB211's things settled down to a very solid airliner. Indeed it may well be, when all the bets are in, that the L1011 will prove to be the safest of all the types so far (at time of writing).
That many are shabby now is a function of TLC - not the design or the airframe. Properly cared for and restored (if you will) she could serve for many many more years yet. The 3 engine concept is a perfect compromise. Remember they only put 8 engines on when 6 wouldn''t produce the urge.
Putting a third motor in the tail is the only logical solution (for 3) and only Lockheed got it correct with the "S" duct. The DC10 was an abomination. However there are structural penalties and she pays them. But at current purchase prices there is a lot of slack for a refit and lots of TLC that would make a wonderful mid range airliner.
It will take courage and foresight to put these babies back into mainstream service. But with oil at $15 a barrel and holding and giveaway prices - it would not be a real gamble. Certainly I would rather take a ride on a Tristar than a A330/340. And when the going gets rough - I would not be clutching the seat arms worrying about the fin - I would be shouting - "Go baby - Go !"
But then I am biased. I have 3000+ hours in those wide seats at the front with the big windows and never had more than a minor heartburn from her. Faster than a 744, stronger than a C130, prettier than a dolphin - what more could you ask?