Good point. I suppose that the trade off is that you loose the "marker posts" from other languages that say to the programmer "Magic happens here, go read the docs" but you gain the power (together with macros) to add features to your language seamlessly.

In fact I think that only 13 "functions" are "magic" in clojure (as in written in java), and the whole rest of the language is written using those 13 functions[1]. That would be like, for example, adding golang's channels to ruby syntax by writing ruby code, without having to drop down to C, which i think is pretty cool.

I also found it very useful in real-life, mostly through having clojure libraries that can do things more seamlessly than similar libraries in other languages. For my last project, I needed to use maybe monad functionality quite often, and having it be as easy to use as the core language in my code was a huge win for my sanity.

[1]: I think some of the data structures are written in java as well, but only for performance reasons.

I find that those syntactic markers make it so much easier to parse the structure of code at a high level, and their lack (or the way they can be embedded inside other expressions) are what has always kept me away from a variety of languages, from Lisp and Forth all the way to CoffeeScript and Haskell.