My favourite thing about swift is actually the core team. Not only are they excellent at jumping in to support users, but they are also very good at looking past community bias' through feature evolution and taking a very pragmatic approach to how swift should evolve over time. Sometimes there are issues with transparency but I believe that is due to being hamstrung by Apple policies rather than them not wanting to be open about certain things (it must drive a few of them crazy).
If we are talking about the language itself, my vote goes (like some others on this thread) to enum, I really miss its flexibility when moving to other languages.