Alfa code
Important! Not for live website use unless you know what you are doing. For development use until testing has been completed and reviewed by a community of peers. If implemented (incorrectly) it can cause site errors. Use at your own risk.
<IfModule mod_rewrite.c>
Options +FollowSymLinks
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L]
RewriteRule category_base/(.*) http://yourdomain.com/$1 [R=301,NC,L]
</IfModule>
Ran into the similar problem of wanting the category base word out of the url.
Am testing the code above in the latest stable version of 2.7. 'category_base' is the category base name from the permalinks settings menu.
Haven't run into any problems with it, but haven't tested it extensively enough to say without a shadow of a doubt it will work all the time and safely. So far the urls of the site that I have tested index.php, categories, single pages as well as comments appear to work.
In the permalink settings in the settings menu the 'custom structure' is selected and set to:
/%category%/%postname%.html