[nv-vn]

Oasis isn't that bad apart from a few options that are tricky to get (or the fact that, as far as I know, there's no sane way to make it install executables to your ocamlfind directory, which makes it fairly unsuitable for PPX extensions). For the most part, it's about as easy/intuitive as using Cabal.

[LeonidasXIV]

Yes, I am using it too, but too bad it is basically unmaintained since its author moved to work for Google. I had hoped it could generate many more files like config for Merlin or Makefiles for build systems than ocamlbuild.

[mercurial]

You may be interested in https://github.com/OCamlPro/opam-user-setup