I wrote the other day about the iPhone version of AIM, and how it takes advantage of push notifications in iPhone 3.0., but since then I've been testing a different chat client that really takes things to the next level: BeejiveIM. You might be put off by the $10 purchase price, but if you're an avid IM fanatic, it will be worth every penny. BeejiveIM supports AIM, Google Chat, MSN, Yahoo!, Facebook and MySpace in a smart layout that makes it the most usable chat app I've tried on the iPhone yet.

The key features that make BeejiveIM a killer app are its support for push notifications, its horizontal keyboard, and the elegant way it organizes open chats. Rather than forcing you to dig through submenus on your buddy list, BeejiveIM puts the buddy list on one screen, and a list of your open chats on another. If someone IMs you while you have a chat open, you can tap once on the number of unread messages to switch between chats. This is right in so many ways, and avoids the clunky feeling of having to go back to your buddy list to switch to another conversation.

Sure, $10 is on the high end of the App Store price range, but there's nothing going that beats BeejiveIM at what it does. It's replaced both the AIM app and the Meebo web app on my home screen.