I started using irssi for IRC a few weeks ago. It is really a nice client, and if you know perl, you can do a lot with it through scripts. The biggest problem that I had with irssi was getting it to auto-connect and auto-identify to servers and then auto-join channels. I was trying to set this stuff up through irssi’s startup file, but was not able to get it to work.
To get irssi to auto-connect and auto-identify with the servers I used
  /server add -auto -network freenode irc.freenode.net 6667 password
and then to get the channels I used
  /channel add -auto #ruby-lang freenode
I set everything up manually inside of irssi and then just used the /save command which writes everything out to the ~/.irssi/config file. When I restarted irssi, everything did what I wanted it to do.