Psi+

Psi Plus is an instant messaging client designed as a simple alternative for IM software with support for the XMPP (Jabber) communication protocol.

Easy installation, standard roster

Getting the application on the system is not difficult as the routine guides you through every step of the operation. At the end of the process you get to make the account settings and tweak the configuration of the connection.
As far as displaying the list of contacts goes, the program is not much different than other XMPP clients. There is the possibility to organize the entries into groups and it provides the number of the friends that are currently online.

Rich customization options

Support for tabs offers the possibility to have multiple chat windows opened in a single screen. Users can also detach the tabs and handle them separately.
The configuration panel of the client shows its flexibility as there are plenty of customization options.
The application can be set to issue pop up notifications on various events such as incoming message, when receiving a file, when the contact at the other end starts typing and even when the contact goes offline or changes the status.
Extended functionality is provided through plug-ins, many of them being provided with the application and just need to be activated. Most of them come with a list of settings that allow customization to your needs.

Conclusion

Psi Plus can be used to connect to any service based on the XMPP communication protocol. It provides a hefty list of options that may seem overwhelming for the less advanced user but more experienced ones should appreciate this level of flexibility.
The support for plug-ins extends its functionality and can greatly improve user interaction.