In that case you might be interested in an IM client that uses the Mozilla XUL runner, GUI written in GTK+ and it's a cross-platform application thus you can run it in GNU/Linux, MS Windows and Mac OSX as well.
*. Easy to use, cleaner interface.
*. It supports protocols such as - AIM, Yahoo, MSN, Google Talk, Facebook and Twitter at the moment.
*. Tabbed interface for managing conversions... it'll be like using a web browser in Tabs rather than in different windows which makes the whole IM thing :) much easier.
*. If you don't like the theme (if it doesn't fit well with your current desktop theme for instance) then simply download the one according to your preference from hundreds of free themes.
*. Drag and drop support (especially for managing contacts).
*. Built in Add-on support - With this, again like with a web browser, you can expand its capabilities as simple as downloading and applying the add-ons.
You can install Instantbird in Ubuntu 11.04 Natty Narwhal by entering the below command in your Terminal window (not sure... but it may work on 10.10/10.04 too).
sudo apt-get install instantbird