Feature request for the Mac OS Vagrant port: please don't copy your executable into /usr/bin when running the installer (and that seems to be the only reason the installer exists at all — it would be better distributed just as a .zip containing the Vagrant directory; I can take it from there). /usr/bin is for system-provided executables, not for applications. I understand the wish to provide an easily-accessible command line executable, but Vagrant users likely know how to modify the path or make an appropriate symlink.
We used to do that, but we received SO MANY complaints that it wasn't instantly available on the PATH, that we symlinked into /usr/bin.
An alternate approach: Mac has some way to hook into shell profile loading so we should be able to inject a script somewhere that amends the PATH. This turns out to be a little crazy on Mac for some reason I don't remember, but should be possible.
Surprisingly, things are better here for Windows: Windows has an API call to both set environmental variables AND send messages to applications to refresh their environmental variables! So, Windows people have somewhat nice things.