Dispatch is a library that I initially found irritating, because in early versions it proved extremely opinionated in it's use of futures and symbolic operators.

However, as time has gone on, I've found that my coding style in Scala has evolved to the point where I want low-level libraries to work in an asynchronous way. There are now also overloaded, human-readable methods for most (if not all) of the symbolic operators.

These days it is my HTTP client of choice.