I'm not particularly attached to Reason syntax myself, but there are some bits of OCaml syntax that do annoy me, such as the right-to-left direction for parametrized types ('a list instead of a more usual list 'a).
As for classes, well... They're not really used outside of specific situations (eg, UI widgets), so it's not really a terribly convenient solution (especially since, for a really useful to_string implementation, you would want the member fields of your class to also implement to_string, so that would mean objects everywhere).