In my code, there are two kinds of places where I get a performance boost by using Clojure:

1. Micro-optimizations, mostly due to JVM and its excellent JIT (the garbage collectors are quite impressive, too, if what you need is predictable response time).

2. Architectural gains: thanks to the Clojure's excellent concurrency support I can make much better use of multiple cores. I get more parallellism, hence better performance on same hardware.

The first kind is cool, because you get it "for free". The second kind is the real game-changer, because non-parallel software only gets you so far in terms of performance, and writing concurrent software is Hard. Clojure makes it much, much easier.

But overall I wouldn't say that Clojure is a performance daemon on a single CPU. You can get performance similar to carefully written Java code. This is good, but you can always do better with C or hand-written assembly on critical sections. But that's not the main advantage: the big thing is that I can write correct Clojure code fast, it runs well enough, and I can easily make use of multiple cores. You can debate micro-benchmarks all you want, but what really counts for me is how quickly (and correctly) I can get from zero to production code that runs fast enough.