Technology review has a nice introductory article on the problems with IM in the enterprise.  Says the article:

But today that promise is stymied by IM software packages that use their own proprietary protocols. "The whole IM scene is as factionalized as Afghanistan," says Rob Batchelder, research director at Gartner, a technology research firm in Stamford, CT.

My main concern is how to use IM behind the firewall with security, logging, etc. at a price that gives an ROI I can see without using a microscope.  I've been playing with jabber lately and have been pretty impressed.  I've haven't even started to consider the interoperability issues.  I guess I don't quite see it yet.  For example:

"Imagine," says Sonu Aggarwal, CEO of Cordant, a Bellvue, WA maker of IM gateway software, "having a contact in your IM buddy list that represents your Delta flight reservation. Rather than having to call an 800-number and digging up your reservation code, that ‘buddy' is your ticket, constantly communicating the status of the reservation."

What I don't get is why I need an IM system to do this for me.  If the airline reservation system is well designed and my reservation has a URI, my aggregator can do that same job without interoperability of IM systems, new ports opened on the firewall, etc.  Maybe I'm high, but I don't see it yet.