FYI, I just changed http://susning.nu/ from plain old CGI to FastCGI and it really makes a change. This is a UseModWiki, just like the old pre-PHP Wikipedias. Plain wiki pages used to load in 2.5 seconds on average. Now they load in less than 0.8 seconds (searches and recent changes take longer).
Q: Why don't I change to the Wikipedia PHP software? A: I've invested too much of my own hacking into the UseModWiki script to abandon it quite yet. And converting to FastCGI turned out to be a piece of cake.
Q: Why don't I run mod_perl instead of stinking old FastCGI technology? A: I use a web hotel with Linux shell login accounts and they don't do mod_perl. I think the reason is that scripts run under mod_perl cannot change user ID to each customer.
Q: Does the site get any traffic? A: It had 180,000 page views in April from 40,000 unique IP addresses, growing at 40 % per month. Many hits are referrals from Google.