I have a tech sitehttp://www.ocmexico.com.mx and i was using myphpnuke for 2 years, but my users and my forums grew very fast and the system went slow and with high CPU usage.
So i decide to migrate the whole database to XOOPS and now my system is running flawless, so if you have a big site with a lots of dialy hits, XOPPS is a must.