In my opinion, JavaFIBS2001 is the best interface for FIBS. It's based on Java, so it can run on every operating system. There are a couple of boards for JavaFIBS, all of them only 2D. Most of them are of a fixed size, and also most of them too small for older eyes, I think. But there is one vectorized board, that can take any size, also filling the whole screen.
The chat window is directly under the board, so it's easy to chat with the opponent and kibitzers.
You can download it here: http://www.fibs.com/~cthulhu/
They are presently working on different new features, so JavaFIBS is the interface which is best taken care of and many improved features can be expected in the future. JavaFIBS used to be shareware, but one can test it as long as one want. I heard, that they won't call it shareware in the near future any more and only ask for optional donations.
As JavaFIBS2001 is based on Java, you also have to install a Java Runtime environment on your computer, if you don't have that yet already.
Hardy 