I've installed plone on three sites now, and have one suggestion:

Add some fields during the installation process to pre-populate the defaults that are normally configurable under "modify language".

Certain defaults don't make any sense and need to be customized immediately.

Examples include:
* pligg.com
* pligg@pligg.com
* any and all email address should be defaulted to whatever I enter at installation (ie: webmaster@mydomain.com).
* Default site description (ie: "mySite allows you to vote on ....")
* Default site name (ie: mySite)
* Default site domain (ie: mysite.com)