Implicits? Compared to Java, Scala is not a simple language. I'd say Scala's complexity is on the order of Haskell + Java syntax with additional glue on top of that.
Not to say this is bad, it just means you need greater discipline when writing software in Scala. A bit like C++ (yes, I went there! :-)).
I'd say this makes Scala slightly more complex than C++ and Ada. Java and Haskell are not in the same league when it comes to complexity (Java because it's simple, Haskell, because it's wickedly well designed so its complexity is completely tractable).
Not to say this is bad, it just means you need greater discipline when writing software in Scala. A bit like C++ (yes, I went there! :-)).