The best IM client gets better.
I've used the free Trillian IM client since I first came across it a year and a half ago. Trillian allows you to connect to all of the popular instant messaging protocols with one program -- Yahoo! Messenger, AOL, MSN, ICQ. They just released a software upgrade on their website to ensure continued compatibility with Yahoo! and MSN. Oh, by the way, Trillian allows you to set up secure IM connections with other persons using Trillian. Think your IM's are private without secure IM? Don't bet on it.