IRC, more than IM, is for me the norm. You go to a chatroom and talk in groups and you have a pretty good log of the conversation. A mutation of IRC is called AltME (altme.com), which lets you comfortably work in IRC style chatrooms, show large amounts of code or text in a single line, create closed and secure chatrooms, export chat logs as HTML and search your logs. It looks like IRC and acts a bit like it, but it handles as much information as a plain text mail and is as fast as IM. It lets you use separate chatrooms for separate topics. As a result, I have about 100 different chatrooms here for different topics. It's persistent: Log off and log on a few days later and see where the conversation has gone since and who has messaged you. It's not yet a fully fledged groupware system, but the chatting part is awesome for me. This is my primary communications form and it works solidly for me and the developers I communicate with. I've been using it since 2003. As a funny side effect, I practically never use email for conversations, only for site registrations, etc.

But it really is only useful for increasing productivity, if you talk to people in the other end, who are used to using it. It takes two skilled IM'ers to make a good conversation or IM session.

I use these rules:

Sender:

1. Talk when you have something important to say that will bring a conversation forward. At any other time, don't say anything.
2. Don't. Speak. One. Word. At a time. To fill. The chatlog. With unnecessary. Crap.
3. Don't expect an answer immediately. Say and forget. Return later to check up the conversation progress. Who cares if the receiver is at his/her desk now? You'll likely get a response later. I think this is one of the reasons people get stressed up over IM, because they don't use it right.
4. If you really, really want a response now, call them or arrange a 30-60 minute chat session within a few hours. Make sure you don't need a response right now, so this won't be an issue. Ask your question in good time, rather than when you must have an answer right now. This also helps eliminating the "oh-crap-I-forgot-to-ask" scenario and it helps the receiver to quietly place a Todo based on that question into his/her GTD system. Remember that you are stressing the receiver and potentially pulling them out of their concentration.

Receiver:

1. Don't answer immediately if you don't want to. Instant messaging does not mean Instant Response and drop-whatever-you're-doing. Phones are made for that kind of nonsense.
2. Don't let your client disturb you with noises and blinking and jumping graphics. Turn that crap off. If you can't, find a different client. Check your client manually along when checking your email.

Generally:

1. Use a persistent chat system that does not require the other end to be online.
2. You can still chat, even if a full day or several days may be required for a response. It's surprisingly easy to maintain a simple conversation thread over a few days. Don't get stressed over it. Relax. Information is not lost with good, persistent chat systems.
3. Multitask. Be asynchronous. I don't find it difficult to quietly and calmly check up on 15-20 conversation threads. Do you? I'm only focusing on a conversation, when I read it.

For me, phone conversations are forbidden with developers and only allowed with friends and family, who can't tell text messaging from a tire iron. Some people around me hate me for that, but this has given me freedom to better focus on correct and accurate communication with many different people. I've had too many bad work experiences of miscommunication, misunderstandings and having to repeat information 5-10 times due to something as simple as a bad phone connection or the urge to smalltalk or change topic, or simply because the guy in the other end informs me of something, when I'm not mentally ready to listen. Text messaging allows me to listen to music as well. That's a good thing. :-)

Sorry for the long post. Just wanted to contribute to a better IM environment.