As Karen said, it depend on the network/channels
As I see it, one of the main advantages of IRC is the channels - you can join #fantasy or #cirinal or #chicks or #freeporn or #physics or #alanis ;b
Off course you might not find a channel like those on all networks, but you can always try another one
I believe most of IM's have something like channels too, but the can't compare with irc chans
Persionally I am a great fan of Tolkien's and i visit #mordor from very long time - I have met many fans there, and we even created a fanclub! (that's the advantage of small countries - you can meet with ppl you know from irc (or Im's ;b))
