Expensive? Sure. Totally essential for messaging hounds? Yup.
$10 sounds steep for a messaging app, and it is—Fring, which is also on this list, can do most of what Beejive can do, for free. The difference is in the execution: Where Fring is serviceable, Beejive shines especially when it comes to multi-account management and busier messaging sessions, and the push implementation is less quirky than its free counterpart's. It's probably overkill for anyone who doesn't spend a few hours a day pecking out instant messages, but hey, some people do that.
From the App Developers: Stay connected to all your instant messaging buddies anywhere you go! BeejiveIM (pronounced \bē-hīv\ IM) keeps you in touch with your friends on AIM®/MobileMe®, MSN®/Windows Live®, Yahoo!®, GoogleTalk®, Facebook, MySpace, ICQ® and Jabber... all at the same time, all on your iPhone or iPod Touch.