Why the rash of new features? AOL is competing with Microsoft not just in the instant messaging space, but also in the realm of advertising-sponsored web applications. The name change from MSN Messenger to Windows Live Messenger was quite deliberate: Microsoft wants all of its IM users to interact with Hotmail, and Windows Live Spaces, and any other "Web 2.0" application they can think of. Adding extra features to AOL Instant Messenger is a way for AOL to compete for these eyeballs.
There is one solid point made that rings true for all instant messaging programs now, except for perhaps IRC. The simplistic days are definitely over, and today's IM clients are veritable hordes of useless (or useless) communication features, from voice and video chat to desktop sharing, blog integration and much more.