If you want to IM from your iPhone, Mundu is your best option because of its interface, stability, and the fact that it will let you chat with users on all four services at once. (Most iPhone IM applications support connection to only one IM service at a time.)

The whole app has a very organic feel that's just right. It's one of the few IM apps I've used on the iPhone where it doesn't feel like you're fighting an interface to make it feel like a desktop app. I also have to give Mundu credit for creating a neat bubbly effect on the chat tab when you've got an unread message. Sometimes it's just the little things that make Web apps more fun to use. In this case, the function is just as good as the form.

This is the best behaving IM client for the iPhone we’ve tested. The interface is responsive, responses are quick to load, and tapping a contact name almost immediately brings up a new chat. We also found the client to be usable over AT&T’s EDGE network, where some other competitors certainly aren’t. ... Chats appear in conversation bubbles, akin to iChat. Away and status messages are neatly displayed, unlike some other clients that do a poor job rendering the text.

The application consists of three different pages: log in, contacts, and chat. Clicking on a contact opens up a new conversation tab in your chat pane. It worked well enough, with a reasonable response time and legible text. It's better than eBuddy (load time issues) and FlickIM (AIM only).

This is typical of the sensational tech/media/business press: an obsession with all things free, all things inflated, and all things unsustainable. Sustainability doesn't mean going back to your investors for another round because you dont have enough to pay your employees because you don't charge for your products.