CPU throttling for fun and profit
I noticed quite an interesting phenomenon with IIS 6 when tweaking with the settings of the server hosting this site amongst a few others. If you limit the CPU usage of the .NET worker processes to a maximum of 95%, all the hosted sites became substantially faster (with 250 simultaneus users). The difference was discernible.
It actually makes sense when you consider that MySQL database server is running on the same box. Apparently MySQL is running on a lower priority (or is CPU throttled) and if the web server eats up all the CPU, web requests with database queries just have to wait. Also the fact that Windows cannot handle scarce recources very well may have something to do with it.
Nevertheless, I'm happy, hope you're happy too.