I used to have the same concern you're expressing, and a few others besides--I've written comments on HN along the lines of "I'm writing Scala that I can't read the next day"--but I got past that stage not too long afterwards, and I find it remarkably predictable and consistent in everyday use.
[1] - this isn't a fair characterization, see deeper in the tree
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).
Why do you say this? vals and immutable data strucutres are clearly emphasized in Scala, so how can you say that FP isn't at its core?
>Scala isn't a pure-FP language, and trying to treat it as one doesn't really...work
Why do you think scalaz concerns itself primarily with enforcing 'purity'? Scalaz' effects library isn't even part of it's core repo.
Coherency/conceptual integrity are things I look for in computing environments they make reasoning things much simpler as logical deductions can be made, I don't find myself doing that with Scala.