I think it'd be a neat feature if there was some way to return to your computer without un-idle-ing Adium, even if you haven't manually set your idle. (Scenario: I set an away and go do something else, then come back later and want to use my computer and see if people have IMed me while I was gone without showing that I'm back by way of un-idling.)
Without knowing how the code would work, maybe this could be a key to hold down when returning (if Adium is frontmost?), or a checkbox in the status prefs ("[] Don't un-idle automatically.").
I've thought about this too. The best I can come up with is that when you come back, it'll un-idle, but the timer will keep internally counting. Then you can manually set idle, and the default value in the time boxes would be the amount of time you would have been idle had you not returned.
