Instant messaging for business purposes?

At my new job one of my duties is process improvement. I am currently researching the viability of using Instant Messaging at work. Can you help by answering some questions I have?

* Do you currently do this and if so, what are your thoughts on it?
* Which service do you use - Yahoo, AIM, WebEx or something else?
* Do you think it increases your level of productivity?
* What specifically do you use it for?
* What's the general thought at your company about it - worth it or not?
* Anything else you'd like to share?

Thanks in advance for your help - 10 points to best answer! :)

We do not use it at our company, but a friend of mine who works at a big company say they use it and it works great for them, if the employees do not abuse it. They use Yahoo, it is a good way to get an instant answer on questions in where you need an immediate answer. My friend's job is to watch to make sure it isn't used for personal business. Otherwise it can be very productive. Our company doesn't use it because the boss thinks everyone will use it for personal business and then no one will be productive. I hope this helps.