This guy puts his finger on precisely the thing that might get me to switch from Common Lisp to Clojure someday. The Java interop aspect is vastly overrated on a technical level. (That's not to say it is overrated in general; it's a marketing master stroke without which the language would have been stillborn.) The concurrency innovations are at best experimental, seem kitchen-sinky, and don't attract me much. But boy do I envy those data structures.
> The concurrency innovations are at best experimental, seem kitchen-sinky,
Could you expand on that statement. I don't think there is anything experimental about Clojure's concurrency features. They are quite robust and build on proven technology.
Clojure has a number of cool new ideas, but many of them are unproven, and only time will tell whether they are truly valuable.
We don't know yet what will become the dominant concurrent programming style(s). For all the talk about the multicore future, nothing has yet emerged that's compellingly better than traditional approaches. Or maybe it has and it just hasn't made its way through the noise into general consciousness; I don't know. Clojure's approach here strikes me as a sort of experimental groping: add several different new concurrency primitives and see what sticks. That aspect seems quite different from the improvements Clojure offers that came from years of experience programming Common Lisp and a resultingly deep intuition about what constructs would make it more comfortable.
Perhaps Clojure has hit the concurrency jackpot and come up with a better way of writing parallel programs. That would be significant. It would even be significant if it offered a better way of writing a particular class of parallel programs. So far, though, I haven't seen convincing evidence of that. I'm more excited about Clojure being an incremental improvement over Common Lisp that is winning over a new audience of hackers.
