The latest instalment in my never-ending quest to find a decent SIP client (see Ubuntu SIP I & Ubuntu SIP II) I came across JITSI (http://jitsi.org/). Since the website looked very interesting and the project seems very well maintained (http://jitsi.org/index.php/Main/Screenshots) I decided to give it a go.
The installation is a breeze with a Ubuntu/Debian package available and the installation also adds the repository to keep the package up to date.
After a few test calls it seems to work very well. The UI is much more intuitive than comparable Ubuntu clients. Looks I found my new default client – nice job Jitsi Team.