Cool, this would have helped me a lot when I was getting started. An idea: You might want to start the README with 'Skeleton is X'. I had to scan around for a while to figure out what your project actually does.
Hey, I looked up your profile and you mention doing some compiler research. HN has no way to 'ping' a user, but I'd be curious what that research entailed...
* It gives you a convenient place to stash extra config options in your project. For example, instead of having to type (and remember!) -tag pkg_oUnit, it's just in the Makefile. You can't forget something that's been saved in a text file!
* It gives you a single point of entry for "other" tools which may be added later -- documentation generation, packaging, installing as a library or Debian package. I personally like all of that recorded in one file so I have to search around less.
* As an expository project, it's helpful to show off clear examples of ocamlbuild itself -- the syntax is different enough that someone just starting out in the language may not be able to grok the documentation enough to just get something running.