Sorry, that was a little more flip than it should have been. Scalaz attempts to wedge into Scala a set of idioms that don't really work well in Scala; as an OO language that's still largely imperative at its core, it's swimming upstream and the code--and the use of that code--is pretty clumsy.
Scala isn't a pure-FP language, and trying to treat it as one doesn't really...work. Square peg, round hole. For me it falls in the "neat hack, but" bucket. That it can be done as Scalaz does is cool, but the practical value of it seems vastly oversold and I'm uncomfortable with the functional-everywhere political viewpoint pushed by some of its leaders (and fortunately Odersky seems opposed to a lot of it, which IMO bodes well for Scala's future).
Scala isn't a pure-FP language, and trying to treat it as one doesn't really...work. Square peg, round hole. For me it falls in the "neat hack, but" bucket. That it can be done as Scalaz does is cool, but the practical value of it seems vastly oversold and I'm uncomfortable with the functional-everywhere political viewpoint pushed by some of its leaders (and fortunately Odersky seems opposed to a lot of it, which IMO bodes well for Scala's future).