Currently the Read Me instructions document the installation of the .component files, whereas Perian now ships a PrefPane?. The instructions should be along the line of 'Double click the Pref Pane to install", similar to Growls:
http://growl.info/documentation/growl-package-install.php
And you might want to mention how the Upgrade process goes (does the PrefPane? automatically overwrite old versions in /Library/Quicktime?)
I'll also note that before double clicking the prefpane I had a 1.0 svn version that I compiled myself a couple weeks ago installed. The prefpane assumed 1.0 was installed when it started up -- i.e. it didn't overwrite my SVN version. I had to click Remove/Install