I have been using Digsby for last couple of days and must say that I am quite impressed by it. Not only does it allow me to login to multi IM networks such as Yahoo, MSN, AIM, GTalk and Jabber but also has a host of other features such as checking mails from Yahoo, Gmail, Hotmail and AOL in addition to checking mails from POP accounts.
Well I also use it for more of twittering now and a little bit for Facebook. You can always follow me on twitter.
Read this post by Karthik to know more as to why should start using Digsby (which actually inspired me to start using it in the first place).