Added support for 'Scopes' using custom find methods if they exist - looks at $model->findMethods (changed filterComponent).
Please add the 'Paginator' component to your AppController or on per controller basis.
*Note there are no result counts for next to scope names (minor detail), not sure how this can be achieved.. yet

Modified Elements/user_info.ctp, to support Authake (Auth+ACL) if that Plugin is loaded.
Also modified ActiveAdminAppController to load default Auth components if Authake is not loaded.

Modified /Layouts/admin.ctp with some annotations and element changes to support scopes element
A few tweaks to /css/admin.css so things fit right, pulled additional CSS for scopes from RoR ActiveAdmin
Made changes to the "Delete Filter" button so it acutally works now (just reloads page).

Tweaked the admin.ctp template, put scopes above the pagination text, and to hides SQL queries if DebugKit plugin is loaded.

Slight tweak to FilterComponent string and text formatting so it now does a
wildcard, LIKE %anything% , instead of finding text that begun with, anything%
Also tweaked PHPDoc (was getting annoyed at my IDE putting squiggles under all of it :[)

Misc changes to ActiveAdmin controller.
Additional filters on models are now supported, relativly small change thanks to the awesome filterComponent
Simply add the variable $aaFilter with an array of field names to models you wan't extra filters on
eg. public $aaFilter = array("start_desc", "start_platform", "end_desc", "end_platform");

Small change to scopes so scopes arn't shown for the dashboard index.
Added support for adding comments against a "resource", it uses the controller name in the url, and the passed param (this in most cases will be the id of the record your looking at)
I've tried to make this robust as possible, but open to improvment as the method I mentioned above using the controller_name+row id may in a edge case
result in comments being logged aginst some random combination.

There is a comments index located at /active_admin/admin_comments so you can see all comments
a link is prodvided to get you back to the item/resource owning the comments.
Author defaults to Admin, because I couldn't work out a reliable way of retrieving the username(differs based on Auth system implmented by the user)

There are predefined filters on the comments index, so you can search comments, by content or by class it came from.

There are options to disable commenting, app wide via ActiveAdmin bootstrap setting
or on a per model basis. Simply add $aaNoComment = true; to models which commenting should be disabled

Finally, data integrity, add this to your app's AppModel, this should remove comments assoicated with a item/resource when it gets deleted
  public function afterDelete()
    {
        //If the active_admin plugin is loaded remove any comments
        if (CakePlugin::loaded("ActiveAdmin")) {
            App::uses('AdminComment', 'ActiveAdmin.Model');
            $aa_comment = new AdminComment();
            $aa_comment->removeComments($this->alias, $this->id);
        }
        return true;
    }

Again this implementation is not perfect, and in my app I have little use for it at current, but it's nice to have some feature like it