If you're wondering what I've been doing lately, here is one of them : Bug 584662 RTL locales support for GNOME Shell.
Since Shell is still rapidly evolving, there are new (RTL related) bugs every now and then, if you want to test this, get gnome-shell from git, apply whatever uncommitted patches from the above bug and, if you find something that doesn't work correctly or doesn't make sense for RTL locales, add comments to that bug.