Key Zope Features that I Find Crucial

Unable to resist a fundamental question, i wrote down several features that i consider key to favoring zope as a web development platform. My focus is on development, not what i see as the more specialized domains of content management or serving high-traffic or static pages, or whatever. I'd be interested in collecting additions to (or deletions from) this list - but only want items that are really fundamental benefits, not just a grab bag...

• extensible in many directions
  • Content management layer, for secured ttw management of extensions
  • High level, secured extensions - ttw products and methods
    • ttw products: zclasses, extension methods
    • ttw methods (dtml, python-, perl-, xlst-, sql-, and-more-methods)
  • lower level extensions - python products, extension methods
  • subterranean extension layer - python is extensible with c, c++, etc
  • core - open-source python, adaptable, growing
• Comprehensive
  • ZServer - multi-protocol scalable network frontend server (http/ftp/webdav,etc)
  • ORB publisher - mapping network addresses to objects
  • ZODB - mapping objects to persistent storage
    • ZEO - sharing single ZODB among multiple Zope instances
  • DocumentTemplate
  • StructuredText
  • BTree flavors
  • DateTime
  • ZLogger
• pluggable - facilitates interconnection ("impedence matching")
• core pieces can be used separately
• Free and open