has anyone used php nuke?

[Xarcell]

Like Ichbin said, the more it was used, the slower it became. Also the module system they had going for it was messy.

[Thurnok]

PhpNuke was and still is a popular CMS.  It's not that difficult once you take the time to learn it.  It's main problem is with updates.  It is still a pretty nice system, though I prefer Mambo/Joomla for ease of use.