I personally have been using Digsby for over a year now. Before that I was a Trillian user and had even paid for pro but whilst Trillian is stable I find it to cluttered and busy these days. Only problem with Digsby is that for some reason Avast does not support it in it's list of IM clients.
Oh and please pay no attention to the Chicken Littles who ran around saying Digsby is evil just because they read it on LifeHacker. Digsby stopped using that particular installer at the start of October last year.