I've heard good things about IM+ for the iPhone, and they've come out with something that looks pretty nice as a universal app. It's one of the featured social apps if I remember correctly. I've not decided to get on it yet, as I am keeping my communication tools on my iPhone for now (except Twitter, which is pretty good on iPad). That, and I'm a BeeJive user on my iPhone. I'm going to wait and see if they come out with a universal update and then decide whether to keep my IMs on my iPhone or not.