Support ControlSocket as well as ControlPort
Quoting from https://trac.vidalia-project.net/ticket/239 :
One suggestion recently was to let Tor have an open ControlSocket on Debian by default, such that only users in a particular group can connect to it and talk to Tor. This means Vidalia will be able to talk to Tor by default, but only if the Vidalia user has the appropriate privileges. This also means that Vidalia won't try to run Tor as the current user, which is a good change.
Tor has supported the ControlSocket option since 0.2.0.3-alpha, but no controllers have ever used it (so it may not still work as advertised). But controlsocket support seems to be one of the main blocking issues in letting Vidalia talk to the Debian tor daemon safely.