Hmmm.. listing the KVIrc features ?
Well... why not ?
Here are some key-phrases that came in my mind.

• User interface
  • Full GUI Based configuration
  • Floatable windows
  • Built-in help browser
  • Themes support (all configurable by GUI or scripting)
  • Pseudo-transparency support (up to the desktop on KDE)
  • Drag & Drop toolbar editing
  • Activity Notifier Pop-Up
  • Status bar with Applet support
  • Unread text mark
  • 14 Languages Translations
• Network
  • Proxy support (SOCKSv4, SOCKSv5, HTTP)
  • Full IPv6 support (also for DCC transfers)
  • SSL support (also over IPv6)
  • Micryption support
• Core
  • Modular architecture: unfrequently used features reside in external modules and are loaded only when necessary
  • Extensibility: a huge API for writing extension modules
  • UNICODE support
• IRC
  • Multi-server connection
  • Notify lists (yes, WATCH is supported)
  • Ignore lists
  • Registered users database
  • Lag meter
  • Configurable logging
  • Standard DCC CHAT and SEND (with resume) support
  • Extended DCC types: VOICE, RSEND, GET, RECV
  • DCC CHAT over SSL
  • DCC bandwidth limit (ability to set it "on the fly")
• Scripting
  • Built-in scripting language interpreter
    • scalars, arrays and hashes...
    • aliases
    • popups
    • events
    • scriptable toolbars
    • Perl support
    • Ability to translate scripts (by the means of the tr() function)
    • ...
  • Objects support in scripting language: yes, now you can do OOP
  • ...

Hmmm...I hope that's enough to make you curious :D