Goban's a very nice program with some unique features, including Rendezvous play and TeX interoperation for printing beautiful Go diagrams. The UI is serviceable, but somewhat less than intuitive, especially with respect to SGF editing.

The main problems we've encountered with Goban, however, are related to local games over Rendezvous. Goban launches a local NNGS server. It seems to be quite difficult at times to get NNGS to "give up" on completed games, and the Goban application has quit unexpectedly several times in the normal course of playing games over Rendezvous, often leaving an orphaned NNGS process which must be terminated by hand before a new one can be spawned.

Even though KGS's CGoban is far from perfect, especially with respect to Macness, there are a few things Goban's developers might be able to learn from CGoban, particularly in terms of editing SGF.

Recommend with reservations. It's the only thing of its kind that is a real Mac application, and does offer a lot of functionality for free. It would just be nice to see Goban be a bit more robust.