And then when a dependency of one of your dependencies is broken agains the latest version. I know some of this has been cleaned up, but it is one of the main reasons I no longer use Scala - I have a rule about how long I'm willing to spend on build issues vs actually writing code, and Scala was always on the wrong side of that.

re: Complexity - At least the signatures for the core collections have been cleaned up a fair amount. That said, the richness of the type system and the prevalence of operator overloading always made it feel like a language you could be really productive in once you knew the language and the current codebase really well, but was really hard to just read through unfamiliar code and know what is going on.