For me, the Terror Tram is something that is insanely cool the first few times you do it... and then it's repeat value diminishes when you realize it changes very little from year to year.
Though I do still appreciate the unique aspects of it (like it or not, it is a one of a kind experience), but for the hard core fan, it's not much of a priority at this point. Though I can imagine it's still quite a draw for a first time visitor.... and it's also got to be a pretty good people eater, from a throughput point of view.