I use default permalinks.
Cpu usage on average 10-20% , global load 0.30 to 0.40 with sometimes traffic spikes.
To get a better SEO result, I wanted to enable fancy permalinks structure with Year/month/day/Posttitle.
After letting it run like that for about 16 hours (second test run, one test run was also done in October 2007, same results).
1) normal setup: Wp-Super cache Half On, default permalinks
2) Fancy permalinks , WP - Super cache FULL ON
3) Fancy permalinks , WP-Super Cache HALF ON
4) Fancy permalinks , WP-Super Cache OFF
1) CPU 10-15% ; Load average 0.07-0.50
2) CPU 60-70% ; Load average 1.20-3.50 (run in this mode for about 10 hours so wp super cache had time to create all cached pages (wp super cache did its job, server load dropped with about 30-40% after creating all pages in a timespan of 4-5 hours)
3) Same cpu and load average as in 2)
4) CPU 70-80% ; Load average went to 6.00-9.00
So I can only conclude that having fancy permalinks enabled costs you up to 4 times more CPU power.
Remark: WP super cache was tested in version 0.8.5 and 0.8.7 , everything was checked multiple times, cached pages were created and present in the correct folders/subfolders . Check on site itself gave the right Page server by cache notes.
No traffic spikes occurred, just my average traffic
So Can this be right? Since I really would like to have fancy permalinks for SEO purposes.... (but having to upgrade my server can easily cost my up to 25-50$ a month extra)