disable clean url's for all logged in users; allow for browser to cache pages.

I think disabling clean url's would be the easiest.
inside boost_boot()/boost_init(), $GLOBALS['conf']['clean_url'] = FALSE if & only if $user->uid != 0.

Just tested and kinda works except that with Image Assist image links return non-clean URL's for anonymous users & Administration menu returns Clean urls for logged in users. Hitting the "Clear cached data" button on the performance page made it work... except that Image Assist links are now incorrect for logged in users. Long story short this is incompatible with drupal's cache_menu & cache_filter tables from my 20 minutes of testing. It would be very useful for sites that never change their html since you could cache it in the browser for like 10 minutes instead of never like it does currently. cache_clear_all(NULL, 'cache_menu'); & cache_clear_all(NULL, 'cache_filter'); Should be called on every page generation to ensure that only anonymous users get clean URLs and logged in users get non-clean URLs. This is only beneficial for a narrow range of sites... if you wish to run like that, be sure to remove this section from your .htaccess file.

  <FilesMatch "(\.html\.gz|\.html)$">
    <IfModule mod_headers.c>
      Header set Expires "Sun, 19 Nov 1978 05:00:00 GMT"
      Header set Cache-Control "no-store, no-cache, must-revalidate, post-check=0, pre-check=0"
    </IfModule>
  </FilesMatch>

and apply this patch.

might as well add a setting for this...

committed