Permalinks

I’m wondering about the performance issues of using post-name for permalinks.

The codex states (http://codex.wordpress.org/Using_Permalinks) ‘for performance reasons, it is not a good idea to start your permalink structure with the category, tag, author, or postname fields’.

Elsewhere I’ve read that cacheing removes much of the problem.

For user-friendlieness, I’d opt for just post-name or category+post-name – but the performance issue concerns me.