I've been a Trillian user for sometime, so its been forever since I upgraded AIM.
But AOL's new release of Triton (at least I think its new, I never noticed it before) has won me over in a day.
First off, the AIM spam problem is over. Everytime a person not on my list IMs me for the first time, it goes in this one "AIM Catcher" box. I can preview the message and decide if I want to open it, trash it, block the user, etc. Now, porn spam (which I haven't gotten yet since I reopened my buddy list) is relegated to a single little box and doesn't get passed to my phone when I'm idle.
Second, what's really neat for Plaxo users is that you can lookup the screenames of your contacts and autoload them. To be honest, there were a lot of people on that list that I'm quite sure wouldn't want IMs from me, so there should be some better or at least more obvious privacy rules around that, but I definitely added a number of screenames of people I e-mail all the time as if we were on IM.
The whole interface is redone, too... it feels very slick. Its a significant improvement over AIM versions of the past and it has me back on AIM and off Trillian. I still think they should let me talk to my few Yahoo! buddies.