The interface resembles the classic user list and chat window appearance, making it intuitive and using the usual Firefox shortcuts for common tasks like switching tabs or closing the current chat window.
The first time it starts, ChatZilla will offer the basic information to start using it, like the needed commands to get help, links to get started with IRC, a FAQ and links to connect directly to one of the many popular networks like Freenode, QuakeNet, EFNet, IRCNet, Dalnet or Undernet.
ChatZilla provides direct support to essential IRC commands for talking with the IRC server and it comes with detailed help for each and every command. Aliases are also supported in ChatZilla so you can define your own shortcut for any command and ease common tasks like a login command or sending a specific message to a channel or a private conversation. DCC is also supported and file transfers are possible in ChatZilla just like in any other IRC client.
Regarding configurability, ChatZilla offers all the friendly-client options, like automatic reconnecting, rejoin when kicked, character encoding, quit message, proxy type, enabled automatically by Firefox, away message, default usermode when connecting, logs. Except for specific IRC settings, ChatZilla also allows to configure appearance settings like fonts or showing a header, add custom aliases, automatically load any custom created Java scripts, text formatting and support for mIRC colours.
Considering most of the time we're using a web browser, using ChatZilla over some other IRC client should be OK, especially if you don't want to open some additional application. Although not by far as powerful as standalone clients like Irssi or XChat, ChatZilla will make the perfect choice for getting and using IRC, especially when working with Firefox all the time is needed.
Install ChatZilla from the Firefox add-ons page