Postname Permalinks in WP 3.3 question

I’d just like to know more about the improved performance for postname permalinks in WP 3.3

I was unable to find any detailed info on the specific Permalink options in WP 3.3?

Are the improvements only for a permalink of /%postname%/ or can you use /%category%/%postname%/ and still benefit from the performance improvements?

I have yet to upgrade, but I’m currently building a site and would like to set it up correctly now, so I get the smoothest transition to 3.3 when I do upgrade.