If your program is divided into threads, having a language like Clojure that makes concurrency easy and lock-free is a wonderful thing, and of course you get some benefit from running on multiple cores, though I don't think that's entirely the point.

If, on the other hand, you're looking for a faster way to map a function across eight million lines in a flat file, using Clojure's map function won't magically make your program run faster (and pmap might not run at all -- you may run out of memory, since pmap isn't truly lazy).

The fact that a Clojure PersistentVector (not a PersistentList) is implemented with a 32-way tree (not 64-way) does not imply that Clojure has abandoned the car/cdr paradigm in favor of conc lists -- it still uses cons, in a more generic form, but still with the same first/rest concept. The trees allow vectors to be inexpensively persistent, so you can have actual practical immutable vectors.