librarian-puppet 1.3.1 and 1.0.8 [changelog] include two important changes. Now there is no need to create a Puppetfile if you have a Modulefile or metadata.json, it will use them by default. Of course you can add a Puppetfile to bring in modules from git, a directory, or github tarballs.
The other change is that all the dependencies’ metadata.json files will be parsed now for transitive dependencies, so it works with the latest Puppet Labs modules and those migrated from the old Modulefile format going forward. That also means that the puppet gem is no longer needed if there are no Modulefile present in your tree of dependencies, which was a source of pain for some users.
The 1.0.x branch is kept updated to run in Ruby 1.8 while 1.1+ requires Ruby 1.9 and uses the Puppet Forge API v3.