Generally, I'd say irc is much more productive than the now-more-typical IM solutions or the webchats of FB/Gmail.
First, it doesn't interrupt me: I'll have it running in one of the tabs in one of my terminal windows. My irc never comes to check on me, I'll go check on irc but only when I want to.
Second, it's persistent: I'm online all the time, I get logs of whatever happens or whoever calls me during my absence, and I can easily review them when I'm back online. Yet I don't need anything but a mere ssh client to access all my messaging.
Third, irc can help me keep it touch with my personal friends but it can keep me in touch with healthy communities as well. Never seen an online chat "room" or IM chat window that had a collective soul as many old irc channels do. I'm a frequent on a few channels, as time permits. I mostly just help (relative) newbies with programming problems these days.