Adium’s approach to statuses is probably the best I have seen in any instant messenger clients. It functions excellently and consistently across all of your chat applications, although it is a little glitchy from time to time. There are heavy customization preferences in the Advanced pane of Adium’s preferences, and you can maintain an endless list of statuses in the Status pane of the preferences.
I recently discovered an often unheard of feature in Adium’s statuses that makes it possible to take a previously saved status and edit it temporarily. To do this, simply click on Statuses in the menu bar, click on the Adium menu bar item, or Control-Click the Adium icon in the dock and select Statuses. After that, hold down the Option key, and click on the status from which you want to create the new, temporary one out of, and a small window will pop up for you to put the information for the status in.
If you’ve ever used a Sony Ericcson phone, they have a feature similar to this for making calls that allows you to edit a phone number before calling.