Guess nobody has an answer... Well, I'll keep searching!

Without hacking the core...
Look for the following code in the "_html_header.inc.php" file for your skin.

<?php skin_content_meta(); /* Charset for static pages */ ?>
	<?php skin_base_tag(); /* Base URL for this skin. You need this to fix relative links! */ ?>
	<?php $Plugins->trigger_event( 'SkinBeginHtmlHead' ); ?>
	<title><?php
		// ------------------------- TITLE FOR THE CURRENT REQUEST -------------------------
		request_title( array(
			'auto_pilot'      => 'seo_title',
		) );
		// ------------------------------ END OF REQUEST TITLE -----------------------------
	?></title>

If your skin is using 'auto_pilot' => 'seo_title', you can try changing it to 'auto_pilot' => 'none' and see if that suits your needs. If not, you can reference the request_title() function in the "/inc/_core/_template.funcs.php" file to see a list of valid parameters that can be passed to that function from your skin's "_html_header.inc.php" file.

Other than than... you're looking at core hacking to achieve what you're looking for.

EDIT: If you change the auto_pilot param to 'none' you'll probably want to modify the title_none param so the main page will have a browser title.

request_title( array(
    'auto_pilot'      => 'none',
	'title_none'	  => $Blog->get( 'name' ),
) );

Using the autopilot none changes nothing, and there doesn't seem to be a parameter to change the categories portion of the header title.

I'm not sure where to hack the files either...