With the release of WordPress version 3.3 there are no longer performance penalties for using the pretty permalink structure. But, the structure that works best for you needs to be based on the type of site you run, not just on generic SEO advice. In this video you’ll see the permalink structures available, which one is right for you, and how to set them up properly. You’ll definitely want to watch this video if you plan to change permalink structures because some changes require you to create special redirects to your pages.
See all videos in the BlogAid WordPress Video Tutorials library.
The link referenced in the video to Joost’s excellent article is