Jabbin is written in C++ and Qt and released under the GNU General Public License. The software's Web site is available in 11 languages. Binary packages are available for Debian, Ubuntu, Fedora, SUSE Linux, and Windows.
For the last three years I've used a Jabber client -- Psi or Gajim -- every day. I used them not only for simple text chatting, but also file transfers and chatting with contacts from other IM protocols such as MSN and ICQ.
Jabbin does all of the above, plus something more: voice over IP calls. This means you can call and speak with a contact that uses the GTalk official client or another Jabber client that is compatible with the Jingle specification instead of typing all the time with the keyboard. There is no need for extra services running in the middle, as Jingle is all client-side.
I have several Jabber accounts on various servers, so I tested Jabbin with a wide variety of Jabber servers, including Google Talk. Jabbin didn't have any problems using any of the servers that I tested it against.
The Jabbin user interface
Jabbin's user interface is mostly a copy of the interface of Psi, a client that is notorious for having one of the worst UIs of any IM clients. Psi's developers recently made some changes to its UI to make it easier to use, but Jabbin forked from Psi before those changes were made and don't care about merging them. One obvious potential improvement -- the button that is visible during voice calls, which now indicates "hang on," should become "hang up".
The main window of Jabbin is by default always on top, a bad habit Jabbin inherited from Psi. The first time Jabbin runs, users must face the account creation window (again copied from Psi), which is a disaster in terms of usability and likely to scare users away. An account creation wizard would work much better.
IM clients should make it easy to type IM text with as few mouse clicks as necessary, but Jabbin doesn't. For example, clicking on the Jabbin window doesn't give focus to the text area; you are expected to click in the window and then click in the text area and start composing your message.
Jabbin does a little better when it comes to security. It lets you encrypt messages with the OpenPGP protocol, thus making it a safe choice for those who care about exchanging sensitive information in real time via instant messaging.
Users migrating from Psi should note that Jabbin uses the same configuration file that Psi does, in the same path. This may be handy for ex-Psi users, but may baffle others, and it's likely to cause problems if Psi decides to change the format of its configuration file and Jabbin goes to read it.
Trying out Jabbin 2.0 beta
Currently Jabbin does VoIP over Jabber using the TINS specification, which one year ago was superseded by the Jingle specification, which was co-written by Jabber Software Foundation and the Google Talk team. Jabbin 2.0 will switch to Jingle, thus making it the first Jingle-compliant open source Jabber client with a GUI that can do VoIP and interoperate with Google Talk. Because Google Talk is expanding into portable devices such as the BlackBerry and the upcoming Sony Mylo, Jabbin users will be able to converse with people running those platforms too. GTalk is expected to interoperate with Skype soon too.
The recently released beta of Jabbin 2.0 is packaged in a proprietary RAR archive -- not something one expects from an open source application, and a choice that probably needs a second thought by the Jabbin team. After installing it, I was able to connect to my Google Talk account (Jabbin 2.0 also adds support for SSL connections), but most of the time I was unable to use VoIP with other contacts that were using the official Google Talk client or Jabbin 2.0, because Jabbin crashed. Twice during my tests I was able to see Google Talk crash too, thanks to, as far as I understand, bad requests from Jabbin.
I also wasn't able to exchange files with Google Talk client users because Google Talk developers chose to implement a custom Jingle-based specification for file transfer which they have not yet published.
Jabbin needs better documentation for its compilation from source procedure, since there is no complete dependency list; parts of it are in the README and INSTALL files and the online forum.
Overall, Jabbin is a good Jabber client. When Jabbin 2.0 comes out of beta, then hopefully VoIP with Jingle will work consistently, as opposed to sometimes. Jabbin will appeal to those who need to use the GTalk VoIP service but also require their client to be cross-platform or open source.
There are major problems with the usability of Jabbin, especially for someone who has a Skype-like background, and even though there is a Getting Started Guide available, it still is not as easy to install the client, fire it up, and talk with contacts without all the first-time hassle. The interface could be massively improved to be more user-friendly. Some saner default settings would make the overall experience less annoying. Jabbin is not so hard to use, but the first impression says the opposite.