I've been using Trillian for the last few years, and it's been OK to use, but as I'm going to have to re-download and re-install it, I may as well check to see if there is anything else I would find better.
What I need the program to do is play nicely with what I'm currently using: MSN, AIM, Yahoo and IRC. I'd also like it to play nicely with things I'm likely to use in the future, such as Jabber. Other stuff I couldn't really care about; I abandoned ICQ years ago (for the last few months I had it I mostly only got spam over it) and don't need it to play nice with Live Journal (I find the Live Journal HTML input page adequate) or Twitter (which I don't use at all).
So far the options are:
Trillian. Advantage: It seems to work reasonably well, and I'm used to it. Disadvantage: It doesn't support Jabber which is apparently what Live Journal use for messaging.
Empathy. Advantage: going by the info. on Wikipedia it supports everything I'm likely to want to use. Disadvantage: the info. on Wikipedia doesn't say which operating systems it runs on, so with my luck I'll go to the trouble of downloading it only to find that it will only run on Linux (which I'll need to try and figure out how to boot off my cigarette lighter to do) or Vista (in which case I'm as stuffed as a roast chicken).
Miranda looks possible but I've never heard of it; its Wikipedia article is barely more than an advertisement and its talk page is no help as to the actual quality of the program either.
Meebo I have heard of but lack of IRC support counts it out completely.
Pidgin I have heard of a lot and had recommended to me but the info. about it on Wikipedia indicates that it has compatibility issues with a lot of the services I'd be using.