I would have thought my 'monster' 6000+ line module would have been considered 'php heavy' enough. Anyway, you got me on a tangent now, and I am looking into some of the cache programs out there now that Zend Cache is some $1500US + (part of Zend Platform).
The idea behind the caches is that optimizer optimizes, but it still needs to convert the english into a more machine readable format. The cache maintains the machine readable part in memory eliminating I/O , optimizing, and conversion.
When and moreso, if I get around to this, I'll be asking which Fantastico offerings require optimizer so I can report any glitches.