First, a bit of history: Pidgin once went by the name GAIM. It was built as an open-source implementation of AOL Instant Messenger, which at the time used a highly proprietary IM protocol. As you may recall, AOL spent years playing a nasty, and ultimately self-defeating, game of cat-and-mouse with rival IM services
Over the past few years, AOL has mellowed considerably. Although AOL has not completely opened the protocol behind AIM and ICQ (known as OSCAR), it has done enough to make interoperability with third-party IM clients a non-issue.
Yet Pidgin is now far more than just an AIM knock-off. It supports more than a dozen of the most widely-used IM protocols, including Apple's Bonjour, .NET Messenger, OSCAR, XMPP (the open protocol used in Google Talk and Jabber) and Yahoo. Pidgin may not support every IM protocol in existence, but the ones it doesn't support generally aren't important enough to worry about, anyway.
Today, I can't imagine using an IM client that lacks this type of multi-protocol support. I do a lot of work-related IM messaging over AIM, although sometimes I have to use Yahoo or .NET Messenger. I also do a lot of personal messaging using Google Talk. Pidgin allows me to manage and access all of these accounts from a single, very clean desktop interface. It doesn't suck down system resources, nag me to buy things or shove tacky ads down my throat.
In short, it's the perfect piece of desktop software for a typical business environment.
I will offer one caveat: If you're looking for multimedia support, including video and voice, then Pidgin probably is not the right choice. The latest release adds limited support for video and voice on XMPP (i.e. Google Talk), but at this point it only works on Linux clients.
Pidgin 2.6.1 also adds support for some additional services, including more reliable Yahoo JAPAN connectivity, and UTF-8 character sets. What it mostly does, however, is incorporate a long list of performance enhancements and bug fixes that make an already reliable IM client even more so.
I know that a lot of people like to use video and voice with their IM services. But these are features associated more with consumer than business IM use. As a result, developers who contribute to Pidgin are simply less inclined to work on such features. (They are, however, beginning to show up, as the evolution of XMPP multimedia support illustrates.)
I suspect that many small-business IM users agree with this approach. They rely heavily upon text messaging and file transfers; other features are curiosities or simply get in the way. Of course, those who use multimedia features occasionally could always fire up a protocol-native IM client when necessary.
For the rest of us, an IM client that makes life simpler and less cluttered is truly a useful tool. If that sounds appealing to you, then I suggest giving Pidgin a try.