In my opinion, ICQ is the first introduction of Whoreware(tm) that I've seen.
Basically, they sold out, and now they're a junk machine full of advertising ****.
Trillian is good if you're needing an ICQ emulato (and everything else, but I hate Trillian, so I'm old-skool using all five programs separately)r.
I myself use AIM and MSN. AIM is the best out of four (ICQ, AIM, YIM, MSN) because even though AOL is infamous for it's **** service, it's kind of surprising that their messanger handles sent/recieved files from your contacts the best (meaning it gives best download/upload speeds).