Arch: pacman -S irssi
Debian: apt-get install irssi
I've used irssi for about 2 moths it's really nice, but you have to take your time to configure it to your needs. I had some problems setting up scripts, though i did follow all the instructions to set them.. anyway that's in the past.
Arch: pacman -S weechat
Debian: apt-get install weechat
I can not say that it's actually better but the defaults that it includes are really nice, i really like the user panel (just like most irc frontends) at the right, it's similar to irssi on the configuration and supports a wide range of languages for scripting.
xchat (gtk frontend)
Arch: pacman -S xchat
Debian: apt-get install xchat
Xchat is a multi-platform IRC chat program. It's simply amazing. While I was trying graphical irc clients, I found that xchat had all the features that anyone could need, it's easy and allows a deeper configuration per server on the matter of username/nick/commands right away. This is suitable for novice users of irc like me.
For more information on xchat http://xchat.org/
In the end i'm going to stick with weechat and xchat, i'll let you know if i run into any real troubles with them. For any questions, just comment.