I thin many of us use this so just to let you know that they released AIM 5.5.3572. Here are some of the features:
Multiple Screen Names
More than one buddy list in the same window.
I used the beta version 5.5.3501. I had no problems with it yet. Im gonna upgrade it now to the final version. Download here: http://www.aim.com/get_aim/win/latest_win.adp