LSD and for my driving (from the mundane to the spirited but no track) I don't miss LSD on my cars.
If one is agressive on the street, taking corners under heavier throttle that 'normal' LSD can minimize unequal tire wear between the right and left rear tires. Sans LSD the inner tire on a turn can spin as the outer tire transfers torque to the inner tire. I'm aware of this shortcoming of a non-LSD car though and avoid whenever possible using too much throttle thus avoiding excessive wear on the right rear tire. (For instance the Turbo's rear tires have just over 12K miles and are quite even in their wear from side to side.)
I think the LSD is robust enough though if one's hammering down on the car all the time and causing the LSD to be active this has to increase the wear/tear on the hardware. Also, I always treated my cars with LSD to more frequent diff fluid servicing. But I never had any problems from the LSD.
If you're an infrequent user of LSD you probably could get by with EBD (electronic braking differential -- IIRC ) where the drivetrain controller applies the brake at the spinning rear wheel to transfer some of its torque to the non-spinning wheel.
I'd be a bit bothered about excessive rear brake wear/tear relying upon this system too often and I don't think I'd like it at all on the track. And I'm not sure how well it works compared to hardware LSD under all conditions.
That said, playing around on Porsche's web site the other day I built both a Cayman S and a Cayman R and for both cars I opted to have LSD. It is a $960 option. Were I to go ahead and get new Cayman (base, S or even an R), or Boxster or ?, I'd spec the car with LSD.
Sincerely,
MarcW.