Some problems I had with IRC during my brief use of it:

1) Finding relevant downloads or chatrooms was nearly impossible, whether due to amazingly irrelevant room descriptions that often advertised files but ended up being nearly or completely empty. Just not worth the effort. I didn't notice any search command that could help me in this case.

2) Finding a chatroom with people talking was also pretty difficult. Even if I was so lucky, chances are they'd ignore you or they'd discuss something so personal no one else would know what the fuck they were talking about. Like >>25 said, there's also a ton of people that go on forever talking about programming or whatever, which is great if you can understand that shit.

3) People seemed to get pissed if you download shit, even though they leave the max downloads really high.

4) Downloads were usually extremely slow for me even with ports open etc., if they worked at all.