I might take a lot of flack for this review, because Adium is universally loved by Mac users, but… well, it's just my opinion, and nobody has to agree with me.
For me, though, Adium is kind of redundant. When I first switched from OS9 to OSX, back in those heady Jaguar days, Adium was the ONLY IM client I would use. AIM, ICQ and Yahoo were bad Carbon ports, MSN was indescribable, and iChat was, er... weird. In addition, Skype was barely a glimmer in anybody's eyes and, though Gizmo was cool, only three people worldwide seemed to ever use it.
At that point, Adium -- and, to a lesser extent, the now defunct Fire and the husk of what was once Proteus -- was a breath of fresh air. It was a convenient, solid, feature-rich application that easily blew away any of the official offerings. It was also extremely customizable and, well... it was very "Mac".
Time marches on, though, and the official clients have gotten better. While this has occurred, it has seemed to me as if Adium continues to tread water, a bit. It is still a very solid application and it is still a very convenient way to keep all your contacts in one list, but it doesn't have video or audio conferencing -- which even MSN has now -- and it falls short in some very basic areas as compared to the official offerings. I have rarely been able to get file transfers to work and, at times, it can act just plain goofy.
Now, that said, I am absolutely not trying to disparage this application. I still love Adium to death and I keep installing updates, but... to be honest, I just don't find myself using it very often anymore. Maybe if I needed to be logged into eight different IM clients, or several different screen names, then I'll start it up, but... for the most part, it sits there looking at me, and just doesn't get used. Which is kind of a shame, because it still has what it has had since day one, back in those OSX 10.2 days -- loads upon loads of amazing potential that it just... doesn't... ever... quite seem... to reach.