* Everything that happens on the talker occurs in a strict
  uniform order.  Everybody sees the same thing.  This is
  good for settling arguments about who said something
  first etc :)
* Most operations involve less typing.  For example, we have
  ; instead of /me, > instead of /msg and < instead of
  /describe.  Also, you can use contractions of usernames 
  and aliases, so even less typing is involved.
* Server + clients (ie, TinyFugue, telnet, netcat) use much
  less CPU time and memory than ircd + BitchX.
* People can't use your nickname.  (I concede that NickServ
  provices this functionality.)
* The outputted text is designed to be easily read and parsable.
  This also involves the use of colour to 'syntax highlight' if
  you like, rather than to make pretty.
* Easier to police, due to the much more sophisticated privilege
  system.
* Easier to customise due to the simple design.
* Talkers don't attract skript-kiddies like IRC servers do.
* Can be accessed without a specific client.  BOFHs are likely
  to block IRC ports.