I've been working with Clojure for a few years now, and the thing I love most about the language is how it nudges developers to write straightforward code. It's maybe closer to a well-structured procedural style than to highly indirect OO or to deeply polymorphic category-theory-inspired typed functional programming. The emphasis on mostly-first-order pure functions composed of other functions, receiving and returning immutable values, makes it easy to untangle even the worst balls of mud, while the well designed set of data-structures (few) and functions operating on them (many) allow for easy and terse expression of everyday data manipulation chores.

If we keep the majority of the code pure and straightforward, we can deal with state and I/O with other constructs, like atoms and records, only where we need to (doing this systematically tends to lead me to some variation of the functional-core/imperative-shell pattern). STM, multimethods, macros and whatnot are cool and have their uses, but after a while I think the really cool thing is how little do we need to resort to fancy stuff and how much is accomplished with just functions and data.