Empathy is certainly awesome. For the bleeding edge stuff, check out the Telepathy PPA on Launchpad.

Quick explanation on why it's called the Telepathy PPA: Telepathy is a generic software framework for instant messaging. Empathy is an instant messaging application; the front-end application that uses Telepathy and makes its technologies usable by end users.

Unfortunately, the experience is a bit different on the desktop; Maemo as a platform was built around Telepathy very early on so everything there is smoothly integrated with it. Telepathy has some really impressive integration technologies coming down the tubes, though, so the desktop (and Maemo) will have some even cooler stuff soon enough. Here is a nice blog post on that:

http://blogs.gnome.org/xclaesse/2008...-empathy-0231/

In a short while, we will be seeing some really impressive desktop applications that can link with people online in the same intuitive way existing instant messaging solutions do (using the same framework, so you don't need to re-enter anything). The Empathy project is pretty close to GNOME, so it'll be happening there first, but Telepathy (the core of it all) is designed to be cross-platform so it should be synonymous with the Linux desktop experience in a few years.
Oh, and completely revolutionary. Nothing else is quite like it.

Nokia also has a nice way of managing People (contacts). For example, being able to choose a person and have all sorts of contact methods available (phone, internet call, IM, email) in the Contacts app. Straight Empathy on most desktop distros (unless you are running Maemo on your desktop :/) does not deliver that, since the email software is not as tightly controlled and it is still a young project so the distributions aren't yet fully committed to it. (I believe Ubuntu is looking really seriously at Empathy now, though).