I was trying to upgrade a single Makefile build system to something better. I just tried ocamlbuild, and omake, and I couldn’t get either to work for a medium sized project. I was hopeful with ocamlbuild but so far just invoking ocamlfind correctly from a Makefile seems to be the way for me. I also upgraded my justmake build system (a Makefile library that has patterns, recursive builds and all the GNU targets via automation, like automake) to use ocaml, it’s a work in progress. I’ll still post justmake later with an example build if I manage it, maybe it will be useful for somebody else.
Justmake used alternative build paths to be compatible with automake/autoconf, it supports specifying a build dir that is, but so if I can get that to work with complex projects that might be useful. The one build tool I’m glad with currently is ocamlfind, it seems fairly reliable.