Well, you can't make everyone happy. Personally, I've started with the C family of languages (C, C++, C#, bit of Java), but after going through Python, Ruby and Elixir I never want to go back to curly braces. The other thing that puts me off is mixing types into the declarations - I treat types as comments and only reach for them if I need to dig deeper; in most of the cases the names of the arguments are self explanatory and types make it really hard for me to parse the function declaration. So instead of this:

  pub fn any(tree: Tree(a), check: fn(a) -> Bool) -> Bool

I'd really prefer something like this (preferably with a syntax highlighter that would grey out the types):

  fn(Tree(a), fn(a) -> Bool) -> Bool
  pub fn any(tree, check)

For some people, including myself, type annotations in Python are killing the spirit of the language. For me, there's no way to format those declarations to look reasonable, except for doing it like in Haskell or Elixir (@type).