> I knew about .rvmrc’s behavior, but I thought that the shell must have provided a hook for the directory changing!

And this, my friends, is another reason to use zsh which calls chpwd() whenever the working directory has changed, which is in fact precisely what the infamous rvm cd script does (I wasn't sure, but just checked).

So those people already running zsh with rvm, you are free of the cd replacement.

Aside of that I still believe that rvm might be a tad bit intrusive and as a Linux user of old, I learned to value the use of distribution packages. But rvm is so darned convenient... :-)